sql server: Graphs, Trees, Hierarchies and Recursive Queries

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--------------------------------------------------------------------- -- Chapter 09 - Graphs, Trees, Hierarchies and Recursive Queries --图,树,层次结构,递归查询 ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Scenarios ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Employees Organizational Chart 组织结构图 ---------------------------------------------------------------------   -- Listing 9-1: DDL & Sample Data for Employees SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.Employees') IS NOT NULL   DROP TABLE dbo.Employees; GO CREATE TABLE dbo.Employees (   empid   INT         NOT NULL PRIMARY KEY,   mgrid   INT         NULL     REFERENCES dbo.Employees,   empname VARCHAR(25) NOT NULL,   salary  MONEY       NOT NULL,   CHECK (empid <> mgrid) );   INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(1, NULL, 'David', $10000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(2, 1, 'Eitan', $7000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(3, 1, 'Ina', $7500.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(4, 2, 'Seraph', $5000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(5, 2, 'Jiru', $5500.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(6, 2, 'Steve', $4500.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(7, 3, 'Aaron', $5000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(8, 5, 'Lilach', $3500.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(9, 7, 'Rita', $3000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(10, 5, 'Sean', $3000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(11, 7, 'Gabriel', $3000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(12, 9, 'Emilia' , $2000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(13, 9, 'Michael', $2000.00); INSERT INTO dbo.Employees(empid, mgrid, empname, salary)   VALUES(14, 9, 'Didi', $1500.00);   CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid); GO   --------------------------------------------------------------------- -- Bill Of Materials (BOM) 物料 ---------------------------------------------------------------------   -- Listing 9-2: DDL & Sample Data for Parts, BOM SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.BOM') IS NOT NULL   DROP TABLE dbo.BOM; GO IF OBJECT_ID('dbo.Parts') IS NOT NULL   DROP TABLE dbo.Parts; GO CREATE TABLE dbo.Parts (   partid   INT         NOT NULL PRIMARY KEY,   partname VARCHAR(25) NOT NULL );   INSERT INTO dbo.Parts(partid, partname) VALUES( 1, 'Black Tea'); INSERT INTO dbo.Parts(partid, partname) VALUES( 2, 'White Tea'); INSERT INTO dbo.Parts(partid, partname) VALUES( 3, 'Latte'); INSERT INTO dbo.Parts(partid, partname) VALUES( 4, 'Espresso'); INSERT INTO dbo.Parts(partid, partname) VALUES( 5, 'Double Espresso'); INSERT INTO dbo.Parts(partid, partname) VALUES( 6, 'Cup Cover'); INSERT INTO dbo.Parts(partid, partname) VALUES( 7, 'Regular Cup'); INSERT INTO dbo.Parts(partid, partname) VALUES( 8, 'Stirrer'); INSERT INTO dbo.Parts(partid, partname) VALUES( 9, 'Espresso Cup'); INSERT INTO dbo.Parts(partid, partname) VALUES(10, 'Tea Shot'); INSERT INTO dbo.Parts(partid, partname) VALUES(11, 'Milk'); INSERT INTO dbo.Parts(partid, partname) VALUES(12, 'Coffee Shot'); INSERT INTO dbo.Parts(partid, partname) VALUES(13, 'Tea Leaves'); INSERT INTO dbo.Parts(partid, partname) VALUES(14, 'Water'); INSERT INTO dbo.Parts(partid, partname) VALUES(15, 'Sugar Bag'); INSERT INTO dbo.Parts(partid, partname) VALUES(16, 'Ground Coffee'); INSERT INTO dbo.Parts(partid, partname) VALUES(17, 'Coffee Beans');   CREATE TABLE dbo.BOM (   partid     INT           NOT NULL REFERENCES dbo.Parts,   assemblyid INT           NULL     REFERENCES dbo.Parts,   unit       VARCHAR(3)    NOT NULL,   qty        DECIMAL(8, 2) NOT NULL,   UNIQUE(partid, assemblyid),   CHECK (partid <> assemblyid) );   INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 1, NULL, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 2, NULL, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 3, NULL, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 4, NULL, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 5, NULL, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 6,    1, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 7,    1, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(10,    1, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(14,    1, 'mL', 230.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 6,    2, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 7,    2, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(10,    2, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(14,    2, 'mL', 205.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(11,    2, 'mL',  25.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 6,    3, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 7,    3, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(11,    3, 'mL', 225.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(12,    3, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 9,    4, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(12,    4, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES( 9,    5, 'EA',   1.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(12,    5, 'EA',   2.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(13,   10, 'g' ,   5.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(14,   10, 'mL',  20.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(14,   12, 'mL',  20.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(16,   12, 'g' ,  15.00); INSERT INTO dbo.BOM(partid, assemblyid, unit, qty)   VALUES(17,   16, 'g' ,  15.00); GO   --------------------------------------------------------------------- -- Road System  道路 ---------------------------------------------------------------------   -- Listing 9-3: DDL & Sample Data for Cities, Roads SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.Roads') IS NOT NULL   DROP TABLE dbo.Roads; GO IF OBJECT_ID('dbo.Cities') IS NOT NULL   DROP TABLE dbo.Cities; GO   CREATE TABLE dbo.Cities (   cityid  CHAR(3)     NOT NULL PRIMARY KEY,   city    VARCHAR(30) NOT NULL,   region  VARCHAR(30) NULL,   country VARCHAR(30) NOT NULL );   INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('ATL', 'Atlanta', 'GA', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('ORD', 'Chicago', 'IL', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('DEN', 'Denver', 'CO', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('IAH', 'Houston', 'TX', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('MCI', 'Kansas City', 'KS', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('LAX', 'Los Angeles', 'CA', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('MIA', 'Miami', 'FL', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('MSP', 'Minneapolis', 'MN', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('JFK', 'New York', 'NY', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('SEA', 'Seattle', 'WA', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('SFO', 'San Francisco', 'CA', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('ANC', 'Anchorage', 'AK', 'USA'); INSERT INTO dbo.Cities(cityid, city, region, country)   VALUES('FAI', 'Fairbanks', 'AK', 'USA');   CREATE TABLE dbo.Roads (   city1       CHAR(3) NOT NULL REFERENCES dbo.Cities,   city2       CHAR(3) NOT NULL REFERENCES dbo.Cities,   distance INT     NOT NULL,   PRIMARY KEY(city1, city2),   CHECK(city1 < city2),   CHECK(distance > 0) );   INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ANC', 'FAI', 359); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'ORD', 715); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'IAH', 800); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'MCI', 805); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'MIA', 665); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('ATL', 'JFK', 865); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'IAH', 1120); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'MCI', 600); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'LAX', 1025); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'MSP', 915); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'SEA', 1335); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('DEN', 'SFO', 1270); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('IAH', 'MCI', 795); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('IAH', 'LAX', 1550); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('IAH', 'MIA', 1190); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('JFK', 'ORD', 795); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('LAX', 'SFO', 385); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MCI', 'ORD', 525); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MCI', 'MSP', 440); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MSP', 'ORD', 410); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('MSP', 'SEA', 2015); INSERT INTO dbo.Roads(city1, city2, distance) VALUES('SEA', 'SFO', 815); GO   --------------------------------------------------------------------- -- Iterations/Recursion ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Subordinates ---------------------------------------------------------------------   -- Listing 9-4: Creation Script for Function fn_subordinates1   --------------------------------------------------------------------- -- Function: fn_subordinates1, Descendants -- -- Input   : @root INT: Manager id -- -- Output  : @Subs Table: id and level of subordinates of --                        input manager (empid = @root) in all levels -- -- Process : * Insert into @Subs row of input manager --           * In a loop, while previous insert loaded more than 0 rows --             insert into @Subs next level of subordinates --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.fn_subordinates1') IS NOT NULL   DROP FUNCTION dbo.fn_subordinates1; GO CREATE FUNCTION dbo.fn_subordinates1(@root AS INT) RETURNS @Subs Table (   empid INT NOT NULL PRIMARY KEY NONCLUSTERED,   lvl   INT NOT NULL,   UNIQUE CLUSTERED(lvl, empid)  -- Index will be used to filter level ) AS BEGIN   DECLARE @lvl AS INT;   SET @lvl = 0;                 -- Initialize level counter with 0     -- Insert root node to @Subs   INSERT INTO @Subs(empid, lvl)     SELECT empid, @lvl FROM dbo.Employees WHERE empid = @root;     WHILE @@rowcount > 0          -- while previous level had rows   BEGIN     SET @lvl = @lvl + 1;        -- Increment level counter       -- Insert next level of subordinates to @Subs     INSERT INTO @Subs(empid, lvl)       SELECT C.empid, @lvl       FROM @Subs AS P           -- P = Parent         JOIN dbo.Employees AS C -- C = Child           ON P.lvl = @lvl - 1   -- Filter parents from previous level           AND C.mgrid = P.empid;   END     RETURN; END GO   -- Node ids of descendants of a given node SELECT empid, lvl FROM dbo.fn_subordinates1(3) AS S;   -- Descendants of a given node SELECT E.empid, E.empname, S.lvl FROM dbo.fn_subordinates1(3) AS S   JOIN dbo.Employees AS E     ON E.empid = S.empid;   -- Leaf nodes underneath a given node SELECT empid FROM dbo.fn_subordinates1(3) AS P WHERE NOT EXISTS   (SELECT * FROM dbo.Employees AS C    WHERE C.mgrid = P.empid);   -- Listing 9-5: Subtree of a Given Root, CTE Solution DECLARE @root AS INT; SET @root = 3;   WITH SubsCTE AS (   -- Anchor member returns root node   SELECT empid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @root     UNION ALL     -- Recursive member returns next level of children   SELECT C.empid, C.empname, P.lvl + 1   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT * FROM SubsCTE;   -- Listing 9-6: Creation Script for Function fn_partsexplosion   --------------------------------------------------------------------- -- Function: fn_partsexplosion, Parts Explosion -- -- Input   : @root INT: Root part id -- -- Output  : @PartsExplosion Table: --              id and level of contained parts of input part --              in all levels -- -- Process : * Insert into @PartsExplosion row of input root part --           * In a loop, while previous insert loaded more than 0 rows --             insert into @PartsExplosion next level of parts --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.fn_partsexplosion') IS NOT NULL   DROP FUNCTION dbo.fn_partsexplosion; GO CREATE FUNCTION dbo.fn_partsexplosion(@root AS INT)   RETURNS @PartsExplosion Table (   partid INT           NOT NULL,   qty    DECIMAL(8, 2) NOT NULL,   unit   VARCHAR(3)    NOT NULL,   lvl    INT           NOT NULL,   n      INT           NOT NULL IDENTITY, -- surrogate key   UNIQUE CLUSTERED(lvl, n)  -- Index will be used to filter lvl ) AS BEGIN   DECLARE @lvl AS INT;   SET @lvl = 0;                  -- Initialize level counter with 0     -- Insert root node to @PartsExplosion   INSERT INTO @PartsExplosion(partid, qty, unit, lvl)     SELECT partid, qty, unit, @lvl     FROM dbo.BOM     WHERE partid = @root;     WHILE @@rowcount > 0           -- while previous level had rows   BEGIN     SET @lvl = @lvl + 1;         -- Increment level counter       -- Insert next level of subordinates to @PartsExplosion     INSERT INTO @PartsExplosion(partid, qty, unit, lvl)       SELECT C.partid, P.qty * C.qty, C.unit, @lvl       FROM @PartsExplosion AS P  -- P = Parent         JOIN dbo.BOM AS C        -- C = Child           ON P.lvl = @lvl - 1    -- Filter parents from previous level           AND C.assemblyid = P.partid;   END     RETURN; END GO   -- Parts Explosion SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl FROM dbo.fn_partsexplosion(2) AS PE   JOIN dbo.Parts AS P     ON P.partid = PE.partid;   -- Listing 9-7: CTE Solution for Parts Explosion DECLARE @root AS INT; SET @root = 2;   WITH PartsExplosionCTE AS (   -- Anchor member returns root part   SELECT partid, qty, unit, 0 AS lvl   FROM dbo.BOM   WHERE partid = @root     UNION ALL     -- Recursive member returns next level of parts   SELECT C.partid, CAST(P.qty * C.qty AS DECIMAL(8, 2)),     C.unit, P.lvl + 1   FROM PartsExplosionCTE AS P     JOIN dbo.BOM AS C       ON C.assemblyid = P.partid ) SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl FROM PartsExplosionCTE AS PE   JOIN dbo.Parts AS P     ON P.partid = PE.partid;   -- Parts Explosion, Aggregating Parts SELECT P.partid, P.partname, PES.qty, PES.unit FROM (SELECT partid, unit, SUM(qty) AS qty       FROM dbo.fn_partsexplosion(2) AS PE       GROUP BY partid, unit) AS PES   JOIN dbo.Parts AS P     ON P.partid = PES.partid;   SELECT P.partid, P.partname, PES.qty, PES.unit FROM (SELECT partid, unit, SUM(qty) AS qty       FROM dbo.fn_partsexplosion(5) AS PE       GROUP BY partid, unit) AS PES   JOIN dbo.Parts AS P     ON P.partid = PES.partid;   -- Listing 9-8: Creation Script for Function fn_subordinates2   --------------------------------------------------------------------- -- Function: fn_subordinates2, --           Descendants with optional level limit -- -- Input   : @root      INT: Manager id --           @maxlevels INT: Max number of levels to return -- -- Output  : @Subs TABLE: id and level of subordinates of --                        input manager in all levels <= @maxlevels -- -- Process : * Insert into @Subs row of input manager --           * In a loop, while previous insert loaded more than 0 rows --             and previous level is smaller than @maxlevels --             insert into @Subs next level of subordinates --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.fn_subordinates2') IS NOT NULL   DROP FUNCTION dbo.fn_subordinates2; GO CREATE FUNCTION dbo.fn_subordinates2   (@root AS INT, @maxlevels AS INT = NULL) RETURNS @Subs TABLE (   empid INT NOT NULL PRIMARY KEY NONCLUSTERED,   lvl   INT NOT NULL,   UNIQUE CLUSTERED(lvl, empid)  -- Index will be used to filter level ) AS BEGIN   DECLARE @lvl AS INT;   SET @lvl = 0;                 -- Initialize level counter with 0   -- If input @maxlevels is NULL, set it to maximum integer   -- to virtually have no limit on levels   SET @maxlevels = COALESCE(@maxlevels, 2147483647);     -- Insert root node to @Subs   INSERT INTO @Subs(empid, lvl)     SELECT empid, @lvl FROM dbo.Employees WHERE empid = @root;     WHILE @@rowcount > 0          -- while previous level had rows     AND @lvl < @maxlevels       -- and previous level < @maxlevels   BEGIN     SET @lvl = @lvl + 1;        -- Increment level counter       -- Insert next level of subordinates to @Subs     INSERT INTO @Subs(empid, lvl)       SELECT C.empid, @lvl       FROM @Subs AS P           -- P = Parent         JOIN dbo.Employees AS C -- C = Child           ON P.lvl = @lvl - 1   -- Filter parents from previous level           AND C.mgrid = P.empid;   END     RETURN; END GO   -- Descendants of a given node, no limit on levels SELECT empid, lvl FROM dbo.fn_subordinates2(3, NULL) AS S;   -- Descendants of a given node, limit 2 levels SELECT empid, lvl FROM dbo.fn_subordinates2(3, 2) AS S;   -- Descendants that are 2 levels underneath a given node SELECT empid FROM dbo.fn_subordinates2(3, 2) AS S WHERE lvl = 2; GO   -- Listing 9-9: Subtree with level limit, CTE Solution, with MAXRECURSION   DECLARE @root AS INT; SET @root = 3;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT * FROM SubsCTE OPTION (MAXRECURSION 2); GO   -- Listing 9-10: Subtree with level limit, CTE Solution, with level column DECLARE @root AS INT, @maxlevels AS INT; SET @root = 3; SET @maxlevels = 2;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid       AND P.lvl < @maxlevels -- limit parent's level ) SELECT * FROM SubsCTE;   --------------------------------------------------------------------- -- Sub-Path ---------------------------------------------------------------------   -- Listing 9-11: Creation Script for Function fn_managers   --------------------------------------------------------------------- -- Function: fn_managers, Ancestors with optional level limit -- -- Input   : @empid INT : Employee id --           @maxlevels : Max number of levels to return -- -- Output  : @Mgrs Table: id and level of managers of --                        input employee in all levels <= @maxlevels -- -- Process : * In a loop, while current manager is not null --             and previous level is smaller than @maxlevels --             insert into @Mgrs current manager, --             and get next level manager --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.fn_managers') IS NOT NULL   DROP FUNCTION dbo.fn_managers; GO CREATE FUNCTION dbo.fn_managers   (@empid AS INT, @maxlevels AS INT = NULL) RETURNS @Mgrs TABLE (   empid INT NOT NULL PRIMARY KEY,   lvl   INT NOT NULL ) AS BEGIN   IF NOT EXISTS(SELECT * FROM dbo.Employees WHERE empid = @empid)     RETURN;      DECLARE @lvl AS INT;   SET @lvl = 0;                 -- Initialize level counter with 0   -- If input @maxlevels is NULL, set it to maximum integer   -- to virtually have no limit on levels   SET @maxlevels = COALESCE(@maxlevels, 2147483647);     WHILE @empid IS NOT NULL      -- while current employee has a manager     AND @lvl <= @maxlevels      -- and previous level < @maxlevels   BEGIN     -- Insert current manager to @Mgrs     INSERT INTO @Mgrs(empid, lvl) VALUES(@empid, @lvl);     SET @lvl = @lvl + 1;        -- Increment level counter     -- Get next level manager     SET @empid = (SELECT mgrid FROM dbo.Employees WHERE empid = @empid);   END     RETURN; END GO   -- Ancestors of a given node, no limit on levels SELECT empid, lvl FROM dbo.fn_managers(8, NULL) AS M;   -- Listing 9-12: Ancestors of a Given Node, CTE Solution   -- Ancestors of a given node, CTE Solution DECLARE @empid AS INT; SET @empid = 8;   WITH MgrsCTE AS (   SELECT empid, mgrid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @empid     UNION ALL     SELECT P.empid, P.mgrid, P.empname, C.lvl + 1   FROM MgrsCTE AS C     JOIN dbo.Employees AS P       ON C.mgrid = P.empid ) SELECT * FROM MgrsCTE;   -- Ancestors of a given node, limit 2 levels SELECT empid, lvl FROM dbo.fn_managers(8, 2) AS M; GO   -- Listing 9-13: Ancestors with Level Limit, CTE Solution DECLARE @empid AS INT, @maxlevels AS INT; SET @empid = 8; SET @maxlevels = 2;   WITH MgrsCTE AS (   SELECT empid, mgrid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @empid     UNION ALL     SELECT P.empid, P.mgrid, P.empname, C.lvl + 1   FROM MgrsCTE AS C     JOIN dbo.Employees AS P       ON C.mgrid = P.empid       AND C.lvl < @maxlevels -- limit child's level ) SELECT * FROM MgrsCTE;   -- Ancestor that is 2 levels above a given node SELECT empid FROM dbo.fn_managers(8, 2) AS M WHERE lvl = 2; GO   --------------------------------------------------------------------- -- Subtree/Subgraph with Path Enumeration ---------------------------------------------------------------------   -- Listing 9-14: Creation Script for Function fn_subordinates3   --------------------------------------------------------------------- -- Function: fn_subordinates3, --           Descendants with optional level limit, --           and path enumeration -- -- Input   : @root      INT: Manager id --           @maxlevels INT: Max number of levels to return -- -- Output  : @Subs TABLE: id, level and materialized ancestors path --                        of subordinates of input manager --                        in all levels <= @maxlevels -- -- Process : * Insert into @Subs row of input manager --           * In a loop, while previous insert loaded more than 0 rows --             and previous level is smaller than @maxlevels: --             - insert into @Subs next level of subordinates --             - calculate a materialized ancestors path for each --               by concatenating current node id to parent's path --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.fn_subordinates3') IS NOT NULL   DROP FUNCTION dbo.fn_subordinates3; GO CREATE FUNCTION dbo.fn_subordinates3   (@root AS INT, @maxlevels AS INT = NULL) RETURNS @Subs TABLE (   empid INT          NOT NULL PRIMARY KEY NONCLUSTERED,   lvl   INT          NOT NULL,   path  VARCHAR(900) NOT NULL   UNIQUE CLUSTERED(lvl, empid)  -- Index will be used to filter level ) AS BEGIN   DECLARE @lvl AS INT;   SET @lvl = 0;                 -- Initialize level counter with 0   -- If input @maxlevels is NULL, set it to maximum integer   -- to virtually have no limit on levels   SET @maxlevels = COALESCE(@maxlevels, 2147483647);     -- Insert root node to @Subs   INSERT INTO @Subs(empid, lvl, path)     SELECT empid, @lvl, '.' + CAST(empid AS VARCHAR(10)) + '.'     FROM dbo.Employees WHERE empid = @root;     WHILE @@rowcount > 0          -- while previous level had rows     AND @lvl < @maxlevels       -- and previous level < @maxlevels   BEGIN     SET @lvl = @lvl + 1;        -- Increment level counter       -- Insert next level of subordinates to @Subs     INSERT INTO @Subs(empid, lvl, path)       SELECT C.empid, @lvl,         P.path + CAST(C.empid AS VARCHAR(10)) + '.'       FROM @Subs AS P           -- P = Parent         JOIN dbo.Employees AS C -- C = Child           ON P.lvl = @lvl - 1   -- Filter parents from previous level           AND C.mgrid = P.empid;   END     RETURN; END GO   -- Return descendants of a given node, along with a materialized path SELECT empid, lvl, path FROM dbo.fn_subordinates3(1, NULL) AS S;   -- Return descendants of a given node, sorted and indented SELECT E.empid, REPLICATE(' | ', lvl) + empname AS empname FROM dbo.fn_subordinates3(1, NULL) AS S   JOIN dbo.Employees AS E     ON E.empid = S.empid ORDER BY path;   -- Listing 9-15: Subtree with Path Enumeration, CTE Solution   -- Descendants of a given node, with Materialized Path, CTE Solution DECLARE @root AS INT; SET @root = 1;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl,     -- Path of root = '.' + empid + '.'     CAST('.' + CAST(empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1,     -- Path of child = parent's path + child empid + '.'     CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, REPLICATE(' | ', lvl) + empname AS empname FROM SubsCTE ORDER BY path;   --------------------------------------------------------------------- -- Sorting ---------------------------------------------------------------------   -- Listing 9-16: Creation Script for Procedure usp_sortsubs   --------------------------------------------------------------------- -- Stored Procedure: usp_sortsubs, --   Descendants with optional level limit and sort values -- -- Input   : @root      INT: Manager id --           @maxlevels INT: Max number of levels to return --           @orderby   sysname: determines sort order -- -- Output  : Rowset: id, level and sort values --                   of subordinates of input manager --                   in all levels <= @maxlevels -- -- Process : * Use a loop to load the desired subtree into #SubsPath --           * For each node, construct a binary sort path --           * The row number represents the node's position among --             siblings based on the input ORDER BY list --           * Load the rows from #SubPath into #SubsSort sorted --             by the binary sortpath --           * IDENTITY values representing the global sort value --             in the subtree will be generated in the target --             #SubsSort table --           * Return all rows from #SubsSort sorted by the --             sort value --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.usp_sortsubs') IS NOT NULL   DROP PROC dbo.usp_sortsubs; GO CREATE PROC dbo.usp_sortsubs   @root      AS INT     = NULL,   @maxlevels AS INT     = NULL,   @orderby   AS sysname = N'empid' AS   SET NOCOUNT ON;   -- #SubsPath is a temp table that will hold binary sort paths CREATE TABLE #SubsPath (   rownum   INT NOT NULL IDENTITY,   nodeid   INT NOT NULL,   lvl      INT NOT NULL,   sortpath VARBINARY(900) NULL ); CREATE UNIQUE CLUSTERED INDEX idx_uc_lvl_empid ON #SubsPath(lvl, nodeid);   -- #SubsPath is a temp table that will hold the final -- integer sort values CREATE TABLE #SubsSort (   nodeid   INT NOT NULL,   lvl      INT NOT NULL,   sortval  INT NOT NULL IDENTITY ); CREATE UNIQUE CLUSTERED INDEX idx_uc_sortval ON #SubsSort(sortval);   -- If @root is not specified, set it to root of the tree IF @root IS NULL   SET @root = (SELECT empid FROM dbo.Employees WHERE mgrid IS NULL); -- If @maxlevels is not specified, set it maximum integer IF @maxlevels IS NULL   SET @maxlevels = 2147483647;   DECLARE @lvl AS INT, @sql AS NVARCHAR(4000); SET @lvl = 0;   -- Load row for input root to #SubsPath -- The root's sort path is simply 1 converted to binary INSERT INTO #SubsPath(nodeid, lvl, sortpath)   SELECT empid, @lvl, CAST(1 AS BINARY(4))   FROM dbo.Employees   WHERE empid = @root;   -- Form a loop to load the next level of suboridnates -- to #SubsPath in each iteration WHILE @@rowcount > 0 AND @lvl < @maxlevels BEGIN   SET @lvl = @lvl + 1;     -- Insert next level of subordinates   -- Initially, just copy parent's path to child   -- Note that IDENTITY values will be generated in #SubsPath   -- based on input order by list   --   -- Then update the path of the employees in the current level   -- to their parent's path + their rownum converted to binary   INSERT INTO #SubsPath(nodeid, lvl, sortpath)     SELECT C.empid, @lvl, P.sortpath     FROM #SubsPath AS P       JOIN dbo.Employees AS C         ON P.lvl = @lvl - 1         AND C.mgrid = P.nodeid     ORDER BY -- determines order of siblings       CASE WHEN @orderby = N'empid'   THEN empid   END,       CASE WHEN @orderby = N'empname' THEN empname END,       CASE WHEN @orderby = N'salary'  THEN salary  END;     UPDATE #SubsPath     SET sortpath = sortpath + CAST(rownum AS BINARY(4))   WHERE lvl = @lvl; END   -- Load the rows from #SubsPath to @SubsSort sorted by the binary -- sort path -- The target identity values in the sortval column will represent -- the global sort value of the nodes within the result subtree INSERT INTO #SubsSort(nodeid, lvl)   SELECT nodeid, lvl FROM #SubsPath ORDER BY sortpath;   -- Return for each node the id, level and sort value SELECT nodeid AS empid, lvl, sortval FROM #SubsSort ORDER BY sortval; GO   -- Get all employees with sort values by empname -- (relying on proc's defaults) EXEC dbo.usp_sortsubs @orderby = N'empname';   -- Get 3 levels of subordinates underneath employee 1 -- with sort values by empname EXEC dbo.usp_sortsubs   @root = 1,   @maxlevels = 3,   @orderby = N'empname'; GO   -- Listing 9-17: Script Returning All Employees, Sorted by empname CREATE TABLE #Subs (   empid    INT NULL,   lvl      INT NULL,   sortval  INT NULL ); CREATE UNIQUE CLUSTERED INDEX idx_uc_sortval ON #Subs(sortval);   -- By empname INSERT INTO #Subs(empid, lvl, sortval)   EXEC dbo.usp_sortsubs     @orderby = N'empname';   SELECT E.empid, REPLICATE(' | ', lvl) + E.empname AS empname FROM #Subs AS S   JOIN dbo.Employees AS E     ON S.empid = E.empid ORDER BY sortval;   -- Listing 9-18: Script Returning All Employees, Sorted by salary TRUNCATE TABLE #Subs;   INSERT INTO #Subs(empid, lvl, sortval)   EXEC dbo.usp_sortsubs     @orderby = N'salary';   SELECT E.empid, salary, REPLICATE(' | ', lvl) + E.empname AS empname FROM #Subs AS S   JOIN dbo.Employees AS E     ON S.empid = E.empid ORDER BY sortval;   -- Cleanup DROP TABLE #Subs GO   -- Listing 9-19: Sorting Hierarchy by empname, CTE Solution DECLARE @root AS INT; SET @root = 1;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl,     -- Path of root is 1 (binary)     CAST(1 AS VARBINARY(MAX)) AS sortpath   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1,     -- Path of child = parent's path + child row number (binary)     P.sortpath + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         ORDER BY C.empname) -- sort col(s)       AS BINARY(4))   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval,   REPLICATE(' | ', lvl) + empname AS empname FROM SubsCTE ORDER BY sortval; GO   -- Listing 9-20: Sorting Hierarchy by salary, CTE Solution DECLARE @root AS INT; SET @root = 1;   WITH SubsCTE AS (   SELECT empid, empname, salary, 0 AS lvl,     -- Path of root = 1 (binary)     CAST(1 AS VARBINARY(MAX)) AS sortpath   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, C.salary, P.lvl + 1,     -- Path of child = parent's path + child row number (binary)     P.sortpath + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         ORDER BY C.salary) -- sort col(s)       AS BINARY(4))   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, salary, ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval,   REPLICATE(' | ', lvl) + empname AS empname FROM SubsCTE ORDER BY sortval;   --------------------------------------------------------------------- -- Cycles ---------------------------------------------------------------------   -- Create a cyclic path UPDATE dbo.Employees SET mgrid = 14 WHERE empid = 1; GO   -- Listing 9-21: Detecting Cycles, CTE Solution DECLARE @root AS INT; SET @root = 1;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl,     CAST('.' + CAST(empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path,     -- Obviously root has no cycle     0 AS cycle   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1,     CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path,     -- Cycle detected if parent's path contains child's id     CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'       THEN 1 ELSE 0 END   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, empname, cycle, path FROM SubsCTE; GO   -- Listing 9-22: Not Pursuing Cycles, CTE Solution DECLARE @root AS INT; SET @root = 1;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl,     CAST('.' + CAST(empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path,     -- Obviously root has no cycle     0 AS cycle   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1,     CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path,     -- Cycle detected if parent's path contains child's id     CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'       THEN 1 ELSE 0 END   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid       AND P.cycle = 0 -- do not pursue branch for parent with cycle ) SELECT empid, empname, cycle, path FROM SubsCTE; GO   -- Listing 9-23: Isolating Cyclic Paths, CTE Solution DECLARE @root AS INT; SET @root = 1;   WITH SubsCTE AS (   SELECT empid, empname, 0 AS lvl,     CAST('.' + CAST(empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path,     -- Obviously root has no cycle     0 AS cycle   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1,     CAST(P.path + CAST(C.empid AS VARCHAR(10)) + '.'          AS VARCHAR(MAX)) AS path,     -- Cycle detected if parent's path contains child's id     CASE WHEN P.path LIKE '%.' + CAST(C.empid AS VARCHAR(10)) + '.%'       THEN 1 ELSE 0 END   FROM SubsCTE AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid       AND P.cycle = 0 ) SELECT path FROM SubsCTE WHERE cycle = 1;   -- Fix cyclic path UPDATE dbo.Employees SET mgrid = NULL WHERE empid = 1;   --------------------------------------------------------------------- -- Materialized Path ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Maintaining Data ---------------------------------------------------------------------   -- Listing 9-24: DDL for Employees with Path SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.Employees') IS NOT NULL   DROP TABLE dbo.Employees; GO CREATE TABLE dbo.Employees (   empid   INT          NOT NULL PRIMARY KEY NONCLUSTERED,   mgrid   INT          NULL     REFERENCES dbo.Employees,   empname VARCHAR(25)  NOT NULL,   salary  MONEY        NOT NULL,   lvl     INT          NOT NULL,   path    VARCHAR(900) NOT NULL UNIQUE CLUSTERED ); CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid); GO   --------------------------------------------------------------------- -- Adding Employees who Manage No One (Leaves) ---------------------------------------------------------------------   -- Listing 9-25: Creation Script for Procedure usp_insertemp   --------------------------------------------------------------------- -- Stored Procedure: usp_insertemp, --   Inserts new employee who manages no one into the table --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.usp_insertemp') IS NOT NULL   DROP PROC dbo.usp_insertemp; GO CREATE PROC dbo.usp_insertemp   @empid   INT,   @mgrid   INT,   @empname VARCHAR(25),   @salary  MONEY AS   SET NOCOUNT ON;   -- Handle case where the new employee has no manager (root) IF @mgrid IS NULL   INSERT INTO dbo.Employees(empid, mgrid, empname, salary, lvl, path)     VALUES(@empid, @mgrid, @empname, @salary,       0, '.' + CAST(@empid AS VARCHAR(10)) + '.'); -- Handle subordinate case (non-root) ELSE   INSERT INTO dbo.Employees(empid, mgrid, empname, salary, lvl, path)     SELECT @empid, @mgrid, @empname, @salary,       lvl + 1, path + CAST(@empid AS VARCHAR(10)) + '.'     FROM dbo.Employees     WHERE empid = @mgrid; GO   -- Listing 9-26: Sample Data for Employees with Path EXEC dbo.usp_insertemp   @empid = 1, @mgrid = NULL, @empname = 'David', @salary = $10000.00; EXEC dbo.usp_insertemp   @empid = 2, @mgrid = 1, @empname = 'Eitan', @salary = $7000.00; EXEC dbo.usp_insertemp   @empid = 3, @mgrid = 1, @empname = 'Ina', @salary = $7500.00; EXEC dbo.usp_insertemp   @empid = 4, @mgrid = 2, @empname = 'Seraph', @salary = $5000.00; EXEC dbo.usp_insertemp   @empid = 5, @mgrid = 2, @empname = 'Jiru', @salary = $5500.00; EXEC dbo.usp_insertemp   @empid = 6, @mgrid = 2, @empname = 'Steve', @salary = $4500.00; EXEC dbo.usp_insertemp   @empid = 7, @mgrid = 3, @empname = 'Aaron', @salary = $5000.00; EXEC dbo.usp_insertemp   @empid = 8, @mgrid = 5, @empname = 'Lilach', @salary = $3500.00; EXEC dbo.usp_insertemp   @empid = 9, @mgrid = 7, @empname = 'Rita', @salary = $3000.00; EXEC dbo.usp_insertemp   @empid = 10, @mgrid = 5, @empname = 'Sean', @salary = $3000.00; EXEC dbo.usp_insertemp   @empid = 11, @mgrid = 7, @empname = 'Gabriel', @salary = $3000.00; EXEC dbo.usp_insertemp   @empid = 12, @mgrid = 9, @empname = 'Emilia', @salary = $2000.00; EXEC dbo.usp_insertemp   @empid = 13, @mgrid = 9, @empname = 'Michael', @salary = $2000.00; EXEC dbo.usp_insertemp   @empid = 14, @mgrid = 9, @empname = 'Didi', @salary = $1500.00; GO   -- Examine data after load SELECT empid, mgrid, empname, salary, lvl, path FROM dbo.Employees ORDER BY path;   --------------------------------------------------------------------- -- Moving a Subtree ---------------------------------------------------------------------   -- Listing 9-27: Creation Script for Procedure usp_movesubtree   --------------------------------------------------------------------- -- Stored Procedure: usp_movesubtree, --   Moves a whole subtree of a given root to a new location --   under a given manager --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.usp_movesubtree') IS NOT NULL   DROP PROC dbo.usp_movesubtree; GO CREATE PROC dbo.usp_movesubtree   @root  INT,   @mgrid INT AS   SET NOCOUNT ON;   BEGIN TRAN;   -- Update level and path of all employees in the subtree (E)   -- Set level =   --   current level + new manager's level - old manager's level   -- Set path =   --   in current path remove old manager's path   --   and substitute with new manager's path   UPDATE E     SET lvl  = E.lvl + NM.lvl - OM.lvl,         path = STUFF(E.path, 1, LEN(OM.path), NM.path)   FROM dbo.Employees AS E          -- E = Employees    (subtree)     JOIN dbo.Employees AS R        -- R = Root         (one row)       ON R.empid = @root       AND E.path LIKE R.path + '%'     JOIN dbo.Employees AS OM       -- OM = Old Manager (one row)       ON OM.empid = R.mgrid     JOIN dbo.Employees AS NM       -- NM = New Manager (one row)       ON NM.empid = @mgrid;       -- Update root's new manager   UPDATE dbo.Employees SET mgrid = @mgrid WHERE empid = @root; COMMIT TRAN; GO   -- Before moving subtree SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path FROM dbo.Employees ORDER BY path;   -- Move Subtree BEGIN TRAN;     EXEC dbo.usp_movesubtree   @root  = 7,   @mgrid = 10;     -- After moving subtree   SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path   FROM dbo.Employees   ORDER BY path;   ROLLBACK TRAN; -- rollback used in order not to apply the change   --------------------------------------------------------------------- -- Removing a Subtree ---------------------------------------------------------------------   -- Before deleteting subtree SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path FROM dbo.Employees ORDER BY path;   -- Delete Subtree BEGIN TRAN;     DELETE FROM dbo.Employees   WHERE path LIKE     (SELECT M.path + '%'      FROM dbo.Employees as M      WHERE M.empid = 7);     -- After deleting subtree   SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, lvl, path   FROM dbo.Employees   ORDER BY path;   ROLLBACK TRAN; -- rollback used in order not to apply the change   --------------------------------------------------------------------- -- Querying Materialized Path ---------------------------------------------------------------------   -- Subtree of a given root SELECT REPLICATE(' | ', E.lvl - M.lvl) + E.empname FROM dbo.Employees AS E   JOIN dbo.Employees AS M     ON M.empid = 3 -- root     AND E.path LIKE M.path + '%' ORDER BY E.path;   -- Subtree of a given root, excluding root SELECT REPLICATE(' | ', E.lvl - M.lvl - 1) + E.empname FROM dbo.Employees AS E   JOIN dbo.Employees AS M     ON M.empid = 3     AND E.path LIKE M.path + '_%' ORDER BY E.path;   -- Leaf nodes under a given root SELECT E.empid, E.empname FROM dbo.Employees AS E   JOIN dbo.Employees AS M     ON M.empid = 3     AND E.path LIKE M.path + '%' WHERE NOT EXISTS   (SELECT *    FROM dbo.Employees AS E2    WHERE E2.mgrid = E.empid);   -- Subtree of a given root, limit number of levels SELECT REPLICATE(' | ', E.lvl - M.lvl) + E.empname FROM dbo.Employees AS E   JOIN dbo.Employees AS M     ON M.empid = 3     AND E.path LIKE M.path + '%'     AND E.lvl - M.lvl <= 2 ORDER BY E.path;   -- Nodes that are n levels under a given root SELECT E.empid, E.empname FROM dbo.Employees AS E   JOIN dbo.Employees AS M     ON M.empid = 3     AND E.path LIKE M.path + '%'     AND E.lvl - M.lvl = 2;   -- Ancestors of a given node (requires a table scan) SELECT REPLICATE(' | ', M.lvl) + M.empname FROM dbo.Employees AS E   JOIN dbo.Employees AS M     ON E.empid = 14     AND E.path LIKE M.path + '%' ORDER BY E.path;   -- Listing 9-28: Creating and Populating Auxiliary Table of Numbers SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.Nums') IS NOT NULL   DROP TABLE dbo.Nums; GO CREATE TABLE dbo.Nums(n INT NOT NULL PRIMARY KEY); DECLARE @max AS INT, @rc AS INT; SET @max = 8000; SET @rc = 1;   INSERT INTO Nums VALUES(1); WHILE @rc * 2 <= @max BEGIN   INSERT INTO dbo.Nums SELECT n + @rc FROM dbo.Nums;   SET @rc = @rc * 2; END   INSERT INTO dbo.Nums   SELECT n + @rc FROM dbo.Nums WHERE n + @rc <= @max; GO   -- Listing 9-29: Creation Script for Function fn_splitpath USE tempdb; GO IF OBJECT_ID('dbo.fn_splitpath') IS NOT NULL   DROP FUNCTION dbo.fn_splitpath; GO CREATE FUNCTION dbo.fn_splitpath(@empid AS INT) RETURNS TABLE AS RETURN   SELECT     n - LEN(REPLACE(LEFT(path, n), '.', '')) AS pos,     CAST(SUBSTRING(path, n + 1,            CHARINDEX('.', path, n+1) - n - 1) AS INT) AS empid   FROM dbo.Employees     JOIN dbo.Nums       ON empid = @empid       AND n < LEN(path)       AND SUBSTRING(path, n, 1) = '.' GO   -- Test fn_splitpath function SELECT pos, empid FROM dbo.fn_splitpath(14);   -- Getting ancestors using fn_splitpath function SELECT REPLICATE(' | ', lvl) + empname FROM dbo.fn_splitpath(14) AS SP   JOIN dbo.Employees AS E     ON E.empid = SP.empid ORDER BY path;   --------------------------------------------------------------------- -- Nested Sets ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Assigning Left and Right Values ---------------------------------------------------------------------   -- Listing 9-30: Producing Binary Sort Paths Representing Nested Sets Relationships USE tempdb; GO -- Create index to speed sorting siblings by empname, empid CREATE UNIQUE INDEX idx_unc_mgrid_empname_empid   ON dbo.Employees(mgrid, empname, empid); GO   DECLARE @root AS INT; SET @root = 1;   -- CTE with two numbers: 1 and 2 WITH TwoNumsCTE AS (   SELECT 1 AS n UNION ALL SELECT 2 ), -- CTE with two binary sort paths for each node: --   One smaller than descendants sort paths --   One greater than descendants sort paths SortPathCTE AS (   SELECT empid, 0 AS lvl, n,     CAST(n AS VARBINARY(MAX)) AS sortpath   FROM dbo.Employees CROSS JOIN TwoNumsCTE   WHERE empid = @root     UNION ALL     SELECT C.empid, P.lvl + 1, TN.n,     P.sortpath + CAST(       (-1+ROW_NUMBER() OVER(PARTITION BY C.mgrid                         -- *** determines order of siblings ***                         ORDER BY C.empname, C.empid))/2*2+TN.n       AS BINARY(4))   FROM SortPathCTE AS P     JOIN dbo.Employees AS C       ON P.n = 1       AND C.mgrid = P.empid     CROSS JOIN TwoNumsCTE AS TN ) SELECT * FROM SortPathCTE ORDER BY sortpath; GO   -- Listing 9-31: CTE Code That Creates Nested Sets Relationships DECLARE @root AS INT; SET @root = 1;   -- CTE with two numbers: 1 and 2 WITH TwoNumsCTE AS (   SELECT 1 AS n UNION ALL SELECT 2 ), -- CTE with two binary sort paths for each node: --   One smaller than descendants sort paths --   One greater than descendants sort paths SortPathCTE AS (   SELECT empid, 0 AS lvl, n,     CAST(n AS VARBINARY(MAX)) AS sortpath   FROM dbo.Employees CROSS JOIN TwoNumsCTE   WHERE empid = @root     UNION ALL     SELECT C.empid, P.lvl + 1, TN.n,     P.sortpath + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         -- *** determines order of siblings ***                         ORDER BY C.empname, C.empid, TN.n)       AS BINARY(4))   FROM SortPathCTE AS P     JOIN dbo.Employees AS C       ON P.n = 1       AND C.mgrid = P.empid     CROSS JOIN TwoNumsCTE AS TN ), -- CTE with Row Numbers Representing sortpath Order SortCTE AS (   SELECT empid, lvl,     ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval   FROM SortPathCTE ), -- CTE with Left and Right Values Representing -- Nested Sets Relationships NestedSetsCTE AS (   SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt   FROM SortCTE   GROUP BY empid, lvl ) SELECT * FROM NestedSetsCTE ORDER BY lft; GO   -- Listing 9-32: Creation Script for the Function fn_empsnestedsets   --------------------------------------------------------------------- -- Function: fn_empsnestedsets, Nested Sets Relationships -- -- Input   : @root INT: Root of subtree -- -- Output  : @NestedSets Table: employee id, level in the subtree, --                              left and right values representing --                              nested sets relationships -- -- Process : * Loads subtree into @SortPath, --             first root, then a level at a time. --             Note: two instances of each employee are loaded; --                   one representing left arm (n = 1), --                   and one representing right (n = 2). --             For each employee and arm, a binary path is constructed, --             representing the nested sets poition. --             The binary path has 4 bytes for each of the employee's --             ancestors. For each ancestor, the 4 bytes represent --             its position in the level (calculated with identity). --             Finally @SortPath will contain a pair of rows for each --             employee along with a sort path represeting the arm's --             nested sets position. --           * Next, the rows from @SortPath are loaded --             into @SortVals, sorted by sortpath. After the load, --             an integer identity column sortval holds sort values --             representing the nested sets position of each arm. --           * The data from @SortVals is grouped by employee --             generating the left and right values for each employee --             in one row. The resultset is loaded into the --             @NestedSets table, which is the function's output. --             --------------------------------------------------------------------- SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.fn_empsnestedsets') IS NOT NULL   DROP FUNCTION dbo.fn_empsnestedsets; GO CREATE FUNCTION dbo.fn_empsnestedsets(@root AS INT)   RETURNS @NestedSets TABLE (   empid INT NOT NULL PRIMARY KEY,   lvl   INT NOT NULL,   lft   INT NOT NULL,   rgt   INT NOT NULL ) AS BEGIN   DECLARE @lvl AS INT;   SET @lvl = 0;     -- @TwoNums: Table Variable with two numbers: 1 and 2   DECLARE @TwoNums TABLE(n INT NOT NULL PRIMARY KEY);   INSERT INTO @TwoNums(n) SELECT 1 AS n UNION ALL SELECT 2;       -- @SortPath: Table Variable with two binary sort paths   -- for each node:   --   One smaller than descendants sort paths   --   One greater than descendants sort paths   DECLARE @SortPath TABLE   (     empid    INT            NOT NULL,     lvl      INT            NOT NULL,     n        INT            NOT NULL,     sortpath VARBINARY(900) NOT NULL,     rownum   INT            NOT NULL IDENTITY,     UNIQUE(lvl, n, empid)   );       -- Load root into @SortPath   INSERT INTO @SortPath(empid, lvl, n, sortpath)     SELECT empid, @lvl, n,       CAST(n AS BINARY(4)) AS sortpath     FROM dbo.Employees CROSS JOIN @TwoNums     WHERE empid = @root     WHILE @@rowcount > 0   BEGIN     SET @lvl = @lvl + 1;       -- Load next level into @SortPath     INSERT INTO @SortPath(empid, lvl, n, sortpath)       SELECT C.empid, @lvl, TN.n, P.sortpath       FROM @SortPath AS P         JOIN dbo.Employees AS C           ON  P.lvl = @lvl - 1           AND P.n = 1           AND C.mgrid = P.empid         CROSS JOIN @TwoNums AS TN       -- *** Determines order of siblings ***       ORDER BY C.empname, C.empid, TN.n;           -- Update sort path to include child's position     UPDATE @SortPath       SET sortpath = sortpath + CAST(rownum AS BINARY(4))     WHERE lvl = @lvl;   END     -- @SortVals: Table Variable with row numbers   -- representing sortpath order   DECLARE @SortVals TABLE   (     empid   INT NOT NULL,     lvl     INT NOT NULL,     sortval INT NOT NULL IDENTITY   )     -- Load data from @SortPath sorted by sortpath   -- to generate sort values   INSERT INTO @SortVals(empid, lvl)     SELECT empid, lvl FROM @SortPath ORDER BY sortpath;     -- Load data into @NestedStes generating left and right   -- values representing nested sets relationships   INSERT INTO @NestedSets(empid, lvl, lft, rgt)     SELECT empid, lvl, MIN(sortval), MAX(sortval)     FROM @SortVals     GROUP BY empid, lvl     RETURN; END GO   -- Test the fn_empsnestedsets function SELECT * FROM dbo.fn_empsnestedsets(1) ORDER BY lft; GO   -- Listing 9-33: Materializing Nested Sets Relationships in a Table SET NOCOUNT ON; USE tempdb; GO   DECLARE @root AS INT; SET @root = 1;   WITH TwoNumsCTE AS (   SELECT 1 AS n UNION ALL SELECT 2 ), SortPathCTE AS (   SELECT empid, 0 AS lvl, n,     CAST(n AS VARBINARY(MAX)) AS sortpath   FROM dbo.Employees CROSS JOIN TwoNumsCTE   WHERE empid = @root     UNION ALL     SELECT C.empid, P.lvl + 1, TN.n,     P.sortpath + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         -- *** determines order of siblings ***                         ORDER BY C.empname, C.empid, TN.n)       AS BINARY(4))   FROM SortPathCTE AS P     JOIN dbo.Employees AS C       ON P.n = 1       AND C.mgrid = P.empid     CROSS JOIN TwoNumsCTE AS TN ), SortCTE AS (   SELECT empid, lvl,     ROW_NUMBER() OVER(ORDER BY sortpath) AS sortval   FROM SortPathCTE ), NestedSetsCTE AS (   SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt   FROM SortCTE   GROUP BY empid, lvl ) SELECT E.empid, E.empname, E.salary, NS.lvl, NS.lft, NS.rgt INTO dbo.EmployeesNS FROM NestedSetsCTE AS NS   JOIN dbo.Employees AS E     ON E.empid = NS.empid;   ALTER TABLE dbo.EmployeesNS ADD PRIMARY KEY NONCLUSTERED(empid); CREATE UNIQUE CLUSTERED INDEX idx_unc_lft_rgt ON dbo.EmployeesNS(lft, rgt); GO   --------------------------------------------------------------------- -- Querying ---------------------------------------------------------------------   -- Descendants of a given root SELECT C.empid, REPLICATE(' | ', C.lvl - P.lvl) + C.empname AS empname FROM dbo.EmployeesNS AS P   JOIN dbo.EmployeesNS AS C     ON P.empid = 3     AND C.lft >= P.lft AND C.rgt <= P.rgt ORDER BY C.lft;   -- Descendants of a given root, limiting 2 levels SELECT C.empid, REPLICATE(' | ', C.lvl - P.lvl) + C.empname AS empname FROM dbo.EmployeesNS AS P   JOIN dbo.EmployeesNS AS C     ON P.empid = 3     AND C.lft >= P.lft AND C.rgt <= P.rgt     AND C.lvl - P.lvl <= 2 ORDER BY C.lft;   -- Leaf nodes under a given root SELECT C.empid, C.empname FROM dbo.EmployeesNS AS P   JOIN dbo.EmployeesNS AS C     ON P.empid = 3     AND C.lft >= P.lft AND C.rgt <= P.rgt     AND C.rgt - C.lft = 1;   -- Count of subordinates of each node SELECT empid, (rgt - lft - 1) / 2 AS cnt,   REPLICATE(' | ', lvl) + empname AS empname FROM dbo.EmployeesNS ORDER BY lft;   -- Ancestors of a given node SELECT P.empid, P.empname, P.lvl FROM dbo.EmployeesNS AS P   JOIN dbo.EmployeesNS AS C     ON C.empid = 14     AND C.lft >= P.lft AND C.rgt <= P.rgt; GO   -- Cleanup DROP TABLE dbo.EmployeesNS; GO   --------------------------------------------------------------------- -- Transitive Closure ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Directed Acyclic Graph (DAG) ---------------------------------------------------------------------   -- Listing 9-34: Transitive Closure of BOM (DAG) WITH BOMTC AS (   -- Return all first-level containment relationships   SELECT assemblyid, partid   FROM dbo.BOM   WHERE assemblyid IS NOT NULL     UNION ALL     -- Return next-level containment relationships   SELECT P.assemblyid, C.partid   FROM BOMTC AS P     JOIN dbo.BOM AS C       ON C.assemblyid = P.partid ) -- Return distinct pairs that have -- transitive containment relationships SELECT DISTINCT assemblyid, partid FROM BOMTC; GO   -- Listing 9-35: Creation Script for the fn_BOMTC UDF IF OBJECT_ID('dbo.fn_BOMTC') IS NOT NULL   DROP FUNCTION dbo.fn_BOMTC; GO   CREATE FUNCTION fn_BOMTC() RETURNS @BOMTC TABLE (   assemblyid INT NOT NULL,   partid     INT NOT NULL,   PRIMARY KEY (assemblyid, partid) ) AS BEGIN   INSERT INTO @BOMTC(assemblyid, partid)     SELECT assemblyid, partid     FROM dbo.BOM     WHERE assemblyid IS NOT NULL     WHILE @@rowcount > 0     INSERT INTO @BOMTC     SELECT P.assemblyid, C.partid     FROM @BOMTC AS P       JOIN dbo.BOM AS C         ON C.assemblyid = P.partid     WHERE NOT EXISTS       (SELECT * FROM @BOMTC AS P2        WHERE P2.assemblyid = P.assemblyid        AND P2.partid = C.partid);     RETURN; END GO   -- Use the fn_BOMTC UDF SELECT assemblyid, partid FROM fn_BOMTC(); GO   -- Listing 9-36: All Paths in BOM WITH BOMPaths AS (   SELECT assemblyid, partid,     1 AS distance, -- distance in first level is 1     -- path in first level is .assemblyid.partid.     '.' + CAST(assemblyid AS VARCHAR(MAX)) +     '.' + CAST(partid     AS VARCHAR(MAX)) + '.' AS path   FROM dbo.BOM   WHERE assemblyid IS NOT NULL     UNION ALL     SELECT P.assemblyid, C.partid,     -- distance in next level is parent's distance + 1     P.distance + 1,     -- path in next level is parent_path.child_partid.     P.path + CAST(C.partid AS VARCHAR(MAX)) + '.'   FROM BOMPaths AS P     JOIN dbo.BOM AS C       ON C.assemblyid = P.partid ) -- Return all paths SELECT * FROM BOMPaths;   -- Listing 9-37: Shortest Paths in BOM WITH BOMPaths -- All paths AS (   SELECT assemblyid, partid,     1 AS distance,     '.' + CAST(assemblyid AS VARCHAR(MAX)) +     '.' + CAST(partid     AS VARCHAR(MAX)) + '.' AS path   FROM dbo.BOM   WHERE assemblyid IS NOT NULL     UNION ALL     SELECT P.assemblyid, C.partid,     P.distance + 1,     P.path + CAST(C.partid AS VARCHAR(MAX)) + '.'   FROM BOMPaths AS P     JOIN dbo.BOM AS C       ON C.assemblyid = P.partid ), BOMMinDist AS -- Minimum distance for each pair (   SELECT assemblyid, partid, MIN(distance) AS mindist   FROM BOMPaths   GROUP BY assemblyid, partid ) -- Shortest path for each pair SELECT BP.* FROM BOMMinDist AS BMD   JOIN BOMPaths AS BP     ON BMD.assemblyid = BP.assemblyid     AND BMD.partid = BP.partid     AND BMD.mindist = BP.distance; GO   --------------------------------------------------------------------- -- Undirected Cyclic Graph ---------------------------------------------------------------------   -- Listing 9-38: Transitive Closure of Roads (Undirected Cyclic Graph) WITH Roads2 -- Two rows for each pair (f-->t, t-->f) AS (   SELECT city1 AS from_city, city2 AS to_city FROM dbo.Roads   UNION ALL   SELECT city2, city1 FROM dbo.Roads ), RoadPaths AS (   -- Return all first-level reachability pairs   SELECT from_city, to_city,     -- path is needed to identify cycles     CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path   FROM Roads2     UNION ALL     -- Return next-level reachability pairs   SELECT F.from_city, T.to_city,     CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))   FROM RoadPaths AS F     JOIN Roads2 AS T       -- if to_city appears in from_city's path, cycle detected       ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'               THEN 1 ELSE 0 END = 0       AND F.to_city = T.from_city ) -- Return Transitive Closure of Roads SELECT DISTINCT from_city, to_city FROM RoadPaths; GO   -- Listing 9-39: Creation Script for the fn_RoadsTC UDF IF OBJECT_ID('dbo.fn_RoadsTC') IS NOT NULL   DROP FUNCTION dbo.fn_RoadsTC; GO   CREATE FUNCTION dbo.fn_RoadsTC() RETURNS @RoadsTC TABLE (   from_city VARCHAR(3) NOT NULL,   to_city   VARCHAR(3) NOT NULL,   PRIMARY KEY (from_city, to_city) ) AS BEGIN   DECLARE @added as INT;     INSERT INTO @RoadsTC(from_city, to_city)     SELECT city1, city2 FROM dbo.Roads;     SET @added = @@rowcount;     INSERT INTO @RoadsTC     SELECT city2, city1 FROM dbo.Roads     SET @added = @added + @@rowcount;     WHILE @added > 0 BEGIN       INSERT INTO @RoadsTC       SELECT DISTINCT TC.from_city, R.city2       FROM @RoadsTC AS TC         JOIN dbo.Roads AS R           ON R.city1 = TC.to_city       WHERE NOT EXISTS         (SELECT * FROM @RoadsTC AS TC2          WHERE TC2.from_city = TC.from_city            AND TC2.to_city = R.city2)         AND TC.from_city <> R.city2;       SET @added = @@rowcount;       INSERT INTO @RoadsTC       SELECT DISTINCT TC.from_city, R.city1       FROM @RoadsTC AS TC         JOIN dbo.Roads AS R           ON R.city2 = TC.to_city       WHERE NOT EXISTS         (SELECT * FROM @RoadsTC AS TC2          WHERE TC2.from_city = TC.from_city            AND TC2.to_city = R.city1)         AND TC.from_city <> R.city1;       SET @added = @added + @@rowcount;   END   RETURN; END GO   -- Use the fn_RoadsTC UDF SELECT * FROM dbo.fn_RoadsTC(); GO   -- Listing 9-40: All paths and distances in Roads (15262 rows) WITH Roads2 AS (   SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads   UNION ALL   SELECT city2, city1, distance FROM dbo.Roads ), RoadPaths AS (   SELECT from_city, to_city, distance,     CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path   FROM Roads2     UNION ALL     SELECT F.from_city, T.to_city, F.distance + T.distance,     CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))   FROM RoadPaths AS F     JOIN Roads2 AS T       ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'               THEN 1 ELSE 0 END = 0       AND F.to_city = T.from_city ) -- Return all paths and distances SELECT * FROM RoadPaths;   -- Listing 9-41: Shortest paths in Roads WITH Roads2 AS (   SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads   UNION ALL   SELECT city2, city1, distance FROM dbo.Roads ), RoadPaths AS (   SELECT from_city, to_city, distance,     CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path   FROM Roads2     UNION ALL     SELECT F.from_city, T.to_city, F.distance + T.distance,     CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))   FROM RoadPaths AS F     JOIN Roads2 AS T       ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'               THEN 1 ELSE 0 END = 0       AND F.to_city = T.from_city ), RoadsMinDist -- Min distance for each pair in TC AS (   SELECT from_city, to_city, MIN(distance) AS mindist   FROM RoadPaths   GROUP BY from_city, to_city ) -- Return shortest paths and distances SELECT RP.* FROM RoadsMinDist AS RMD   JOIN RoadPaths AS RP     ON RMD.from_city = RP.from_city     AND RMD.to_city = RP.to_city     AND RMD.mindist = RP.distance; GO   -- Listing 9-42: Load Shortest Road Paths Into a Table WITH Roads2 AS (   SELECT city1 AS from_city, city2 AS to_city, distance FROM dbo.Roads   UNION ALL   SELECT city2, city1, distance FROM dbo.Roads ), RoadPaths AS (   SELECT from_city, to_city, distance,     CAST('.' + from_city + '.' + to_city + '.' AS VARCHAR(MAX)) AS path   FROM Roads2     UNION ALL     SELECT F.from_city, T.to_city, F.distance + T.distance,     CAST(F.path + T.to_city + '.' AS VARCHAR(MAX))   FROM RoadPaths AS F     JOIN Roads2 AS T       ON CASE WHEN F.path LIKE '%.' + T.to_city + '.%'               THEN 1 ELSE 0 END = 0       AND F.to_city = T.from_city ), RoadsMinDist AS (   SELECT from_city, to_city, MIN(distance) AS mindist   FROM RoadPaths   GROUP BY from_city, to_city ) SELECT RP.* INTO dbo.RoadPaths FROM RoadsMinDist AS RMD   JOIN RoadPaths AS RP     ON RMD.from_city = RP.from_city     AND RMD.to_city = RP.to_city     AND RMD.mindist = RP.distance;   CREATE UNIQUE CLUSTERED INDEX idx_uc_from_city_to_city   ON dbo.RoadPaths(from_city, to_city); GO   -- Return shortest path between Los Angeles and New York SELECT * FROM dbo.RoadPaths WHERE from_city = 'LAX' AND to_city = 'JFK'; GO   -- Listing 9-43: Creation Script for the fn_RoadsTC UDF IF OBJECT_ID('dbo.fn_RoadsTC') IS NOT NULL   DROP FUNCTION dbo.fn_RoadsTC; GO CREATE FUNCTION dbo.fn_RoadsTC() RETURNS @RoadsTC TABLE (   uniquifier INT          NOT NULL IDENTITY,   from_city  VARCHAR(3)   NOT NULL,   to_city    VARCHAR(3)   NOT NULL,   distance   INT          NOT NULL,   route      VARCHAR(MAX) NOT NULL,   PRIMARY KEY (from_city, to_city, uniquifier) ) AS BEGIN   DECLARE @added AS INT;     INSERT INTO @RoadsTC     SELECT city1 AS from_city, city2 AS to_city, distance,       '.' + city1 + '.' + city2 + '.'     FROM dbo.Roads;     SET @added = @@rowcount;     INSERT INTO @RoadsTC     SELECT city2, city1, distance, '.' + city2 + '.' + city1 + '.'     FROM dbo.Roads;     SET @added = @added + @@rowcount;     WHILE @added > 0 BEGIN     INSERT INTO @RoadsTC       SELECT DISTINCT TC.from_city, R.city2,         TC.distance + R.distance, TC.route + city2 + '.'       FROM @RoadsTC AS TC         JOIN dbo.Roads AS R           ON R.city1 = TC.to_city       WHERE NOT EXISTS         (SELECT * FROM @RoadsTC AS TC2          WHERE TC2.from_city = TC.from_city            AND TC2.to_city = R.city2            AND TC2.distance <= TC.distance + R.distance)         AND TC.from_city <> R.city2;       SET @added = @@rowcount;       INSERT INTO @RoadsTC       SELECT DISTINCT TC.from_city, R.city1,         TC.distance + R.distance, TC.route + city1 + '.'       FROM @RoadsTC AS TC         JOIN dbo.Roads AS R           ON R.city2 = TC.to_city       WHERE NOT EXISTS         (SELECT * FROM @RoadsTC AS TC2          WHERE TC2.from_city = TC.from_city            AND TC2.to_city = R.city1            AND TC2.distance <= TC.distance + R.distance)         AND TC.from_city <> R.city1;       SET @added = @added + @@rowcount;   END   RETURN; END GO   -- Return shortest paths and distances SELECT from_city, to_city, distance, route FROM (SELECT from_city, to_city, distance, route,         RANK() OVER (PARTITION BY from_city, to_city                      ORDER BY distance) AS rk       FROM dbo.fn_RoadsTC()) AS RTC WHERE rk = 1; GO   -- Cleanup DROP TABLE dbo.RoadPaths; GO

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https://www.microsoftpressstore.com/store/inside-microsoft-sql-server-2008-t-sql-querying-9780735626034

 

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--随机行 SELECT TOP(1)  * FROM dbo.Employees ORDER BY RAND(); GO   SELECT TOP(1)  * FROM dbo.Employees  ORDER BY checksum(NEWID()); GO

　

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--------------------------------------------------------------------- -- Analytical Ranking Functions ---------------------------------------------------------------------   -- Listing 4-3: Creating and Populating the Sales Table SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.Sales') IS NOT NULL   DROP TABLE dbo.Sales; GO   CREATE TABLE dbo.Sales (   empid VARCHAR(10) NOT NULL PRIMARY KEY,   mgrid VARCHAR(10) NOT NULL,   qty   INT         NOT NULL );   INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('A', 'Z', 300); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('B', 'X', 100); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('C', 'X', 200); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('D', 'Y', 200); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('E', 'Z', 250); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('F', 'Z', 300); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('G', 'X', 100); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('H', 'Y', 150); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('I', 'X', 250); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('J', 'Z', 100); INSERT INTO dbo.Sales(empid, mgrid, qty) VALUES('K', 'Y', 200);   CREATE INDEX idx_qty_empid ON dbo.Sales(qty, empid); CREATE INDEX idx_mgrid_qty_empid ON dbo.Sales(mgrid, qty, empid); GO     -- Rank and dense rank 排名和密集排名 SELECT empid, qty,   (SELECT COUNT(*) FROM dbo.Sales AS S2    WHERE S2.qty < S1.qty) + 1 AS rnk,   (SELECT COUNT(DISTINCT qty) FROM dbo.Sales AS S2    WHERE S2.qty < S1.qty) + 1 AS drnk FROM dbo.Sales AS S1 ORDER BY qty;   --------------------------------------------------------------------- -- NTILE ---------------------------------------------------------------------   --------------------------------------------------------------------- -- NTILE Function, SQL Server 2005 ---------------------------------------------------------------------   -- NTILE SELECT empid, qty,   NTILE(3) OVER(ORDER BY qty, empid) AS tile FROM dbo.Sales ORDER BY qty, empid;   -- Descriptive Tiles SELECT empid, qty,   CASE NTILE(3) OVER(ORDER BY qty, empid)     WHEN 1 THEN 'low'     WHEN 2 THEN 'meduim'     WHEN 3 THEN 'high'   END AS lvl FROM dbo.Sales ORDER BY qty, empid;   -- Ranges of Quantities Corresponding to each Category WITH Tiles AS (   SELECT empid, qty,     NTILE(3) OVER(ORDER BY qty, empid) AS tile   FROM dbo.Sales ) SELECT tile, MIN(qty) AS lb, MAX(qty) AS hb FROM Tiles GROUP BY tile ORDER BY tile;   --------------------------------------------------------------------- -- Other Solutions to NTILE ---------------------------------------------------------------------   -- NTILE, even Distribution of Remainder DECLARE @numtiles AS INT; SET @numtiles = 3;   SELECT empid, qty,   CAST((rn - 1) / tilesize + 1 AS INT) AS tile FROM (SELECT empid, qty, rn,         1.*numrows/@numtiles AS tilesize       FROM (SELECT empid, qty,               (SELECT COUNT(*) FROM dbo.Sales AS S2                WHERE S2.qty < S1.qty                   OR S2.qty = S1.qty                      AND S2.empid <= S1.empid) AS rn,               (SELECT COUNT(*) FROM dbo.Sales) AS numrows             FROM dbo.Sales AS S1) AS D1) AS D2 ORDER BY qty, empid; GO   -- NTILE, pre-2005, remainder added to first groups DECLARE @numtiles AS INT; SET @numtiles = 9;   SELECT empid, qty,   CASE     WHEN rn <= (tilesize+1) * remainder       THEN (rn-1) / (tilesize+1) + 1     ELSE (rn - remainder - 1) / tilesize + 1   END AS tile FROM (SELECT empid, qty, rn,         numrows/@numtiles AS tilesize,         numrows%@numtiles AS remainder       FROM (SELECT empid, qty,               (SELECT COUNT(*) FROM dbo.Sales AS S2                 WHERE S2.qty < S1.qty                   OR S2.qty = S1.qty                       AND S2.empid <= S1.empid) AS rn,               (SELECT COUNT(*) FROM dbo.Sales) AS numrows             FROM dbo.Sales AS S1) AS D1) AS D2 ORDER BY qty, empid; GO

　　http://tsql.solidq.com/SampleContent/InsideTSQLQuerying2005_06.pdf

https://math.ucsd.edu/~crypto/Monty/montybg.html