sql script: Graphs, Trees, Hierarchies and Recursive Queries

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--------------------------------------------------------------------- -- Inside Microsoft SQL Server 2008: T-SQL Querying (MSPress, 2009) -- Chapter 12 - Graphs, Trees, Hierarchies and Recursive Queries -- Copyright Itzik Ben-Gan, 2009 -- All Rights Reserved ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Scenarios ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Employees Organizational Chart ---------------------------------------------------------------------   -- Listing 12-1: 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),   (2,  1,    'Eitan'  ,  $7000.00),   (3,  1,    'Ina'    ,  $7500.00),   (4,  2,    'Seraph' ,  $5000.00),   (5,  2,    'Jiru'   ,  $5500.00),   (6,  2,    'Steve'  ,  $4500.00),   (7,  3,    'Aaron'  ,  $5000.00),   (8,  5,    'Lilach' ,  $3500.00),   (9,  7,    'Rita'   ,  $3000.00),   (10, 5,    'Sean'   ,  $3000.00),   (11, 7,    'Gabriel',  $3000.00),   (12, 9,    'Emilia' ,  $2000.00),   (13, 9,    'Michael',  $2000.00),   (14, 9,    'Didi'   ,  $1500.00);   CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid); GO   --------------------------------------------------------------------- -- Bill Of Materials (BOM) ---------------------------------------------------------------------   -- Listing 12-2: 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'      ),   ( 2, 'White Tea'      ),   ( 3, 'Latte'          ),   ( 4, 'Espresso'       ),   ( 5, 'Double Espresso'),   ( 6, 'Cup Cover'      ),   ( 7, 'Regular Cup'    ),   ( 8, 'Stirrer'        ),   ( 9, 'Espresso Cup'   ),   (10, 'Tea Shot'       ),   (11, 'Milk'           ),   (12, 'Coffee Shot'    ),   (13, 'Tea Leaves'     ),   (14, 'Water'          ),   (15, 'Sugar Bag'      ),   (16, 'Ground Coffee'  ),   (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),   ( 2, NULL, 'EA',   1.00),   ( 3, NULL, 'EA',   1.00),   ( 4, NULL, 'EA',   1.00),   ( 5, NULL, 'EA',   1.00),   ( 6,    1, 'EA',   1.00),   ( 7,    1, 'EA',   1.00),   (10,    1, 'EA',   1.00),   (14,    1, 'mL', 230.00),   ( 6,    2, 'EA',   1.00),   ( 7,    2, 'EA',   1.00),   (10,    2, 'EA',   1.00),   (14,    2, 'mL', 205.00),   (11,    2, 'mL',  25.00),   ( 6,    3, 'EA',   1.00),   ( 7,    3, 'EA',   1.00),   (11,    3, 'mL', 225.00),   (12,    3, 'EA',   1.00),   ( 9,    4, 'EA',   1.00),   (12,    4, 'EA',   1.00),   ( 9,    5, 'EA',   1.00),   (12,    5, 'EA',   2.00),   (13,   10, 'g' ,   5.00),   (14,   10, 'mL',  20.00),   (14,   12, 'mL',  20.00),   (16,   12, 'g' ,  15.00),   (17,   16, 'g' ,  15.00); GO   --------------------------------------------------------------------- -- Road System ---------------------------------------------------------------------   -- Listing 12-3: 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'),   ('ORD', 'Chicago', 'IL', 'USA'),   ('DEN', 'Denver', 'CO', 'USA'),   ('IAH', 'Houston', 'TX', 'USA'),   ('MCI', 'Kansas City', 'KS', 'USA'),   ('LAX', 'Los Angeles', 'CA', 'USA'),   ('MIA', 'Miami', 'FL', 'USA'),   ('MSP', 'Minneapolis', 'MN', 'USA'),   ('JFK', 'New York', 'NY', 'USA'),   ('SEA', 'Seattle', 'WA', 'USA'),   ('SFO', 'San Francisco', 'CA', 'USA'),   ('ANC', 'Anchorage', 'AK', 'USA'),   ('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),   ('ATL', 'ORD',  715),   ('ATL', 'IAH',  800),   ('ATL', 'MCI',  805),   ('ATL', 'MIA',  665),   ('ATL', 'JFK',  865),   ('DEN', 'IAH', 1120),   ('DEN', 'MCI',  600),   ('DEN', 'LAX', 1025),   ('DEN', 'MSP',  915),   ('DEN', 'SEA', 1335),   ('DEN', 'SFO', 1270),   ('IAH', 'MCI',  795),   ('IAH', 'LAX', 1550),   ('IAH', 'MIA', 1190),   ('JFK', 'ORD',  795),   ('LAX', 'SFO',  385),   ('MCI', 'ORD',  525),   ('MCI', 'MSP',  440),   ('MSP', 'ORD',  410),   ('MSP', 'SEA', 2015),   ('SEA', 'SFO',  815); GO   --------------------------------------------------------------------- -- Iterations/Recursion ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Subordinates ---------------------------------------------------------------------   -- Creation Script for Function Subordinates1   --------------------------------------------------------------------- -- Function: 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.Subordinates1') IS NOT NULL   DROP FUNCTION dbo.Subordinates1; GO CREATE FUNCTION dbo.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 按级数筛选时用的索引 ) AS BEGIN   DECLARE @lvl AS INT = 0;      -- Initialize level counter with 0 初始化计数器为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 当上一级存在行   BEGIN     SET @lvl = @lvl + 1;        -- Increment level counter 递增级数计数器       -- 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 筛选上一级的父节点           AND C.mgrid = P.empid;   END     RETURN; END GO   -- Node ids of descendants of a given node返回员工ID3的下属 SELECT empid, lvl FROM dbo.Subordinates1(3) AS S;   -- Descendants of a given node SELECT E.empid, E.empname, S.lvl FROM dbo.Subordinates1(3) AS S   JOIN dbo.Employees AS E     ON E.empid = S.empid;   -- Leaf nodes underneath a given node SELECT empid FROM dbo.Subordinates1(3) AS P WHERE NOT EXISTS   (SELECT * FROM dbo.Employees AS C    WHERE C.mgrid = P.empid);   -- Subtree of a Given Root, CTE Solution 锚点成员，返回 DECLARE @root AS INT = 3; WITH Subs 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 Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT * FROM Subs;             -- Creation Script for Function PartsExplosion   --------------------------------------------------------------------- -- Function: PartsExplosion, Parts Explosion 零件分解 另：产品零件组合 -- -- 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.PartsExplosion') IS NOT NULL   DROP FUNCTION dbo.PartsExplosion; GO CREATE FUNCTION dbo.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 代理键   UNIQUE CLUSTERED(lvl, n)  -- Index will be used to filter lvl 用索引号LVL进行筛选 ) AS BEGIN   DECLARE @lvl AS INT = 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   UDF CTE    返回White Tea 的零部件 SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl FROM dbo.PartsExplosion(2) AS PE   JOIN dbo.Parts AS P     ON P.partid = PE.partid;       -- CTE Solution for Parts Explosion DECLARE @root AS INT = 2;   WITH PartsExplosion 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 PartsExplosion AS P     JOIN dbo.BOM AS C       ON C.assemblyid = P.partid ) SELECT P.partid, P.partname, PE.qty, PE.unit, PE.lvl FROM PartsExplosion AS PE   JOIN dbo.Parts AS P     ON P.partid = PE.partid; GO     -- Parts Explosion, Aggregating Parts SELECT P.partid, P.partname, PES.qty, PES.unit FROM (SELECT partid, unit, SUM(qty) AS qty       FROM dbo.PartsExplosion(2) AS PE       GROUP BY partid, unit) AS PES   JOIN dbo.Parts AS P     ON P.partid = PES.partid; GO   SELECT P.partid, P.partname, PES.qty, PES.unit FROM (SELECT partid, unit, SUM(qty) AS qty       FROM dbo.PartsExplosion(5) AS PE       GROUP BY partid, unit) AS PES   JOIN dbo.Parts AS P     ON P.partid = PES.partid; GO   -- Creation Script for Function Subordinates2   --------------------------------------------------------------------- -- Function: 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.Subordinates2') IS NOT NULL   DROP FUNCTION dbo.Subordinates2; GO CREATE FUNCTION dbo.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 = 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.Subordinates2(3, NULL) AS S;   -- Descendants of a given node, limit 2 levels SELECT empid, lvl FROM dbo.Subordinates2(3, 2) AS S;   -- Descendants that are 2 levels underneath a given node 返回员工3以下第二级下属 SELECT empid FROM dbo.Subordinates2(3, 2) AS S WHERE lvl = 2; GO   -- Subtree with level limit, CTE Solution, with MAXRECURSION   DECLARE @root AS INT = 3;   WITH Subs AS (   SELECT empid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1   FROM Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT * FROM Subs OPTION (MAXRECURSION 2); GO   -- Subtree with level limit, CTE Solution, with level column DECLARE @root AS INT = 3, @maxlevels AS INT = 2;   WITH Subs AS (   SELECT empid, empname, 0 AS lvl   FROM dbo.Employees   WHERE empid = @root     UNION ALL     SELECT C.empid, C.empname, P.lvl + 1   FROM Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT * FROM Subs WHERE lvl <= @maxlevels;   --------------------------------------------------------------------- -- Sub-Path ---------------------------------------------------------------------   -- Creation Script for Function Managers   --------------------------------------------------------------------- -- Function: Managers, Ancestors with optional level limit 具有可选级数限制的祖先（父） -- -- 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.Managers') IS NOT NULL   DROP FUNCTION dbo.Managers; GO CREATE FUNCTION dbo.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 = 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 返回员工8的所有级别的经理 SELECT empid, lvl FROM dbo.Managers(8, NULL) AS M;   -- Ancestors of a Given Node, CTE Solution   -- Ancestors of a given node, CTE Solution DECLARE @empid AS INT = 8;   WITH Mgrs 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 Mgrs AS C     JOIN dbo.Employees AS P       ON C.mgrid = P.empid ) SELECT * FROM Mgrs;   -- Ancestors of a given node, limit 2 levels SELECT empid, lvl FROM dbo.Managers(8, 2) AS M; GO   -- Ancestors with Level Limit, CTE Solution DECLARE @empid AS INT = 8, @maxlevels AS INT = 2;   WITH Mgrs 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 Mgrs AS C     JOIN dbo.Employees AS P       ON C.mgrid = P.empid ) SELECT * FROM Mgrs WHERE lvl <= @maxlevels;   -- Ancestor that is 2 levels above a given node SELECT empid FROM dbo.Managers(8, 2) AS M WHERE lvl = 2; GO   --------------------------------------------------------------------- -- Subtree/Subgraph with Path Enumeration 带有路径枚举的子图/子树 ---------------------------------------------------------------------   -- Creation Script for Function Subordinates3   --------------------------------------------------------------------- -- Function: Subordinates3, --           Descendants with optional level limit,具有可选级数的下属，以及路径枚举 --           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.Subordinates3') IS NOT NULL   DROP FUNCTION dbo.Subordinates3; GO CREATE FUNCTION dbo.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 = 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.Subordinates3(1, NULL) AS S;   -- Return descendants of a given node, sorted and indented SELECT E.empid, REPLICATE(' | ', lvl) + empname AS empname FROM dbo.Subordinates3(1, NULL) AS S   JOIN dbo.Employees AS E     ON E.empid = S.empid ORDER BY path;   -- Subtree with Path Enumeration, CTE Solution   -- Descendants of a given node, with Materialized Path, CTE Solution DECLARE @root AS INT = 1;   WITH Subs 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))   FROM Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, REPLICATE(' | ', lvl) + empname AS empname FROM Subs ORDER BY path;   --------------------------------------------------------------------- -- Sorting ---------------------------------------------------------------------   -- Sorting Hierarchy by empname, CTE Solution DECLARE @root AS INT = 1;   WITH Subs AS (   SELECT empid, empname, 0 AS lvl,     -- Path of root is 1 (binary)     CAST(1 AS VARBINARY(MAX)) AS sort_path   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.sort_path + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         ORDER BY C.empname) -- sort col(s)       AS BINARY(4))   FROM Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval,   REPLICATE(' | ', lvl) + empname AS empname FROM Subs ORDER BY sortval; GO   -- Sorting Hierarchy by salary, CTE Solution DECLARE @root AS INT = 1;   WITH Subs AS (   SELECT empid, empname, salary, 0 AS lvl,     -- Path of root = 1 (binary)     CAST(1 AS VARBINARY(MAX)) AS sort_path   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.sort_path + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         ORDER BY C.salary) -- sort col(s)       AS BINARY(4))   FROM Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, salary, ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval,   REPLICATE(' | ', lvl) + empname AS empname FROM Subs ORDER BY sortval;   --------------------------------------------------------------------- -- Cycles 环 ---------------------------------------------------------------------   -- Create a cyclic path UPDATE dbo.Employees SET mgrid = 14 WHERE empid = 1; GO   -- Detecting Cycles, CTE Solution DECLARE @root AS INT = 1;   WITH Subs 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)),     -- 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 Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid ) SELECT empid, empname, cycle, path FROM Subs; GO   -- Not Pursuing Cycles, CTE Solution DECLARE @root AS INT = 1;   WITH Subs 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)),     -- 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 Subs 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 Subs; GO   -- Isolating Cyclic Paths, CTE Solution DECLARE @root AS INT = 1;   WITH Subs 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)),     -- 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 Subs AS P     JOIN dbo.Employees AS C       ON C.mgrid = P.empid       AND P.cycle = 0 ) SELECT path FROM Subs WHERE cycle = 1;   -- Fix cyclic path UPDATE dbo.Employees SET mgrid = NULL WHERE empid = 1;   --------------------------------------------------------------------- -- Materialized Path ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Custom Materialized Path ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Maintaining Data ---------------------------------------------------------------------   -- 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) 具体化路径 ---------------------------------------------------------------------   -- Creation Script for Procedure AddEmp   --------------------------------------------------------------------- -- Stored Procedure: AddEmp, --   Inserts new employee who manages no one into the table --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.AddEmp') IS NOT NULL   DROP PROC dbo.AddEmp; GO CREATE PROC dbo.AddEmp   @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   -- Sample Data for Employees with Path EXEC dbo.AddEmp   @empid = 1, @mgrid = NULL, @empname = 'David', @salary = $10000.00; EXEC dbo.AddEmp   @empid = 2, @mgrid = 1, @empname = 'Eitan', @salary = $7000.00; EXEC dbo.AddEmp   @empid = 3, @mgrid = 1, @empname = 'Ina', @salary = $7500.00; EXEC dbo.AddEmp   @empid = 4, @mgrid = 2, @empname = 'Seraph', @salary = $5000.00; EXEC dbo.AddEmp   @empid = 5, @mgrid = 2, @empname = 'Jiru', @salary = $5500.00; EXEC dbo.AddEmp   @empid = 6, @mgrid = 2, @empname = 'Steve', @salary = $4500.00; EXEC dbo.AddEmp   @empid = 7, @mgrid = 3, @empname = 'Aaron', @salary = $5000.00; EXEC dbo.AddEmp   @empid = 8, @mgrid = 5, @empname = 'Lilach', @salary = $3500.00; EXEC dbo.AddEmp   @empid = 9, @mgrid = 7, @empname = 'Rita', @salary = $3000.00; EXEC dbo.AddEmp   @empid = 10, @mgrid = 5, @empname = 'Sean', @salary = $3000.00; EXEC dbo.AddEmp   @empid = 11, @mgrid = 7, @empname = 'Gabriel', @salary = $3000.00; EXEC dbo.AddEmp   @empid = 12, @mgrid = 9, @empname = 'Emilia', @salary = $2000.00; EXEC dbo.AddEmp   @empid = 13, @mgrid = 9, @empname = 'Michael', @salary = $2000.00; EXEC dbo.AddEmp   @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 ---------------------------------------------------------------------   -- Creation Script for Procedure MoveSubtree   --------------------------------------------------------------------- -- Stored Procedure: MoveSubtree, --   Moves a whole subtree of a given root to a new location --   under a given manager --------------------------------------------------------------------- USE tempdb; GO IF OBJECT_ID('dbo.MoveSubtree') IS NOT NULL   DROP PROC dbo.MoveSubtree; GO CREATE PROC dbo.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 移动子树 BEGIN TRAN;     EXEC dbo.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  删除子树 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 查询 ---------------------------------------------------------------------   -- 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;   -- 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 = 1000000, @rc AS INT = 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   -- Creation Script for Function SplitPath USE tempdb; GO IF OBJECT_ID('dbo.SplitPath') IS NOT NULL   DROP FUNCTION dbo.SplitPath; GO CREATE FUNCTION dbo.SplitPath(@empid AS INT) RETURNS TABLE AS RETURN   SELECT     ROW_NUMBER() OVER(ORDER BY 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 SplitPath function SELECT pos, empid FROM dbo.SplitPath(14);   -- Getting ancestors using SplitPath function SELECT REPLICATE(' | ', lvl) + empname FROM dbo.SplitPath(14) AS SP   JOIN dbo.Employees AS E     ON E.empid = SP.empid ORDER BY path;   -- Presentation SELECT REPLICATE(' | ', lvl) + empname FROM dbo.Employees ORDER BY path;   --------------------------------------------------------------------- -- Materialized Path with the HIERARCHYID Datatype 使用HIERARCHYID数据类型的具体化路径 --HIERARCHYID类型提供了下列方法和属性：GetLevel,GetRoot,GetAncestor,GetDescendant,GetReparentedValue,IsDescendantOf,ToString,Parse,Read,Write ---------------------------------------------------------------------   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,   hid     HIERARCHYID NOT NULL,   lvl AS hid.GetLevel() PERSISTED,   empname VARCHAR(25) NOT NULL,   salary  MONEY       NOT NULL,   mgrid INT NULL );   CREATE UNIQUE CLUSTERED INDEX idx_depth_first ON dbo.Employees(hid); CREATE UNIQUE INDEX idx_breadth_first ON dbo.Employees(lvl, hid); CREATE UNIQUE INDEX idx_empid ON dbo.Employees(empid); GO   --------------------------------------------------------------------- -- Maintaining Data ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Adding Employees ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Stored Procedure: AddEmp, --   Inserts new employee who manages no one into the table --------------------------------------------------------------------- IF OBJECT_ID('dbo.AddEmp', 'P') IS NOT NULL   DROP PROC dbo.AddEmp; GO CREATE PROC dbo.AddEmp   @empid   AS INT,   @mgrid   AS INT,   @empname AS VARCHAR(25),   @salary  AS MONEY AS   DECLARE   @hid            AS HIERARCHYID,   @mgr_hid        AS HIERARCHYID,   @last_child_hid AS HIERARCHYID;   BEGIN TRAN     IF @mgrid IS NULL     SET @hid = hierarchyid::GetRoot();   ELSE   BEGIN     SET @mgr_hid = (SELECT hid FROM dbo.Employees WITH (UPDLOCK)                     WHERE empid = @mgrid);     SET @last_child_hid =       (SELECT MAX(hid) FROM dbo.Employees        WHERE hid.GetAncestor(1) = @mgr_hid);     SET @hid = @mgr_hid.GetDescendant(@last_child_hid, NULL);   END     INSERT INTO dbo.Employees(empid, hid, empname, salary)     VALUES(@empid, @hid, @empname, @salary);     COMMIT TRAN GO   EXEC dbo.AddEmp @empid =  1, @mgrid = NULL, @empname = 'David'  , @salary = $10000.00; EXEC dbo.AddEmp @empid =  2, @mgrid =    1, @empname = 'Eitan'  , @salary = $7000.00; EXEC dbo.AddEmp @empid =  3, @mgrid =    1, @empname = 'Ina'    , @salary = $7500.00; EXEC dbo.AddEmp @empid =  4, @mgrid =    2, @empname = 'Seraph' , @salary = $5000.00; EXEC dbo.AddEmp @empid =  5, @mgrid =    2, @empname = 'Jiru'   , @salary = $5500.00; EXEC dbo.AddEmp @empid =  6, @mgrid =    2, @empname = 'Steve'  , @salary = $4500.00; EXEC dbo.AddEmp @empid =  7, @mgrid =    3, @empname = 'Aaron'  , @salary = $5000.00; EXEC dbo.AddEmp @empid =  8, @mgrid =    5, @empname = 'Lilach' , @salary = $3500.00; EXEC dbo.AddEmp @empid =  9, @mgrid =    7, @empname = 'Rita'   , @salary = $3000.00; EXEC dbo.AddEmp @empid = 10, @mgrid =    5, @empname = 'Sean'   , @salary = $3000.00; EXEC dbo.AddEmp @empid = 11, @mgrid =    7, @empname = 'Gabriel', @salary = $3000.00; EXEC dbo.AddEmp @empid = 12, @mgrid =    9, @empname = 'Emilia' , @salary = $2000.00; EXEC dbo.AddEmp @empid = 13, @mgrid =    9, @empname = 'Michael', @salary = $2000.00; EXEC dbo.AddEmp @empid = 14, @mgrid =    9, @empname = 'Didi'   , @salary = $1500.00; GO   SELECT hid, hid.ToString() AS path, lvl, empid, empname, salary FROM dbo.Employees ORDER BY hid;     SELECT * FROM dbo.Employees --------------------------------------------------------------------- -- Moving a Subtree ---------------------------------------------------------------------   SELECT   CAST('/1/1/2/3/2/' AS HIERARCHYID).GetReparentedValue('/1/1/', '/2/1/4/').ToString();   --------------------------------------------------------------------- -- Stored Procedure: MoveSubtree, 移动子树 --   Moves a whole subtree of a given root to a new location --   under a given manager --------------------------------------------------------------------- IF OBJECT_ID('dbo.MoveSubtree') IS NOT NULL   DROP PROC dbo.MoveSubtree; GO CREATE PROC dbo.MoveSubtree   @empid    AS INT,   @new_mgrid AS INT AS   DECLARE   @old_root AS HIERARCHYID,   @new_root AS HIERARCHYID,   @new_mgr_hid AS HIERARCHYID;   BEGIN TRAN     SET @new_mgr_hid = (SELECT hid FROM dbo.Employees WITH (UPDLOCK)                       WHERE empid = @new_mgrid);   SET @old_root = (SELECT hid FROM dbo.Employees                    WHERE empid = @empid);     -- First, get a new hid for the subtree root employee that moves   SET @new_root = @new_mgr_hid.GetDescendant     ((SELECT MAX(hid)       FROM dbo.Employees       WHERE hid.GetAncestor(1) = @new_mgr_hid),      NULL);     -- Next, reparent all descendants of employee that moves   UPDATE dbo.Employees     SET hid = hid.GetReparentedValue(@old_root, @new_root)   WHERE hid.IsDescendantOf(@old_root) = 1;   COMMIT TRAN GO   SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path FROM dbo.Employees ORDER BY hid;   BEGIN TRAN     EXEC dbo.MoveSubtree     @empid    = 5,     @new_mgrid = 9;     SELECT empid, REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path   FROM dbo.Employees   ORDER BY hid;   ROLLBACK TRAN GO   --------------------------------------------------------------------- -- Querying 查询 ---------------------------------------------------------------------   -- Subtree SELECT E.empid, E.empname FROM dbo.Employees AS M   JOIN dbo.Employees AS E     ON M.empid = 3     AND E.hid.IsDescendantOf(M.hid) = 1 WHERE E.lvl - M.lvl <= 3;   -- Path 路径 SELECT M.empid, M.empname FROM dbo.Employees AS M   JOIN dbo.Employees AS E     ON E.empid = 14     AND E.hid.IsDescendantOf(M.hid) = 1;   -- Direct Subordinates 直接下属 SELECT E.empid, E.empname FROM dbo.Employees AS M   JOIN dbo.Employees AS E     ON M.empid = 2     AND E.hid.GetAncestor(1) = M.hid;   -- Leaf nodes 叶子节点 SELECT empid, empname FROM dbo.Employees AS M WHERE NOT EXISTS   (SELECT * FROM dbo.Employees AS E    WHERE E.hid.GetAncestor(1) = M.hid);   -- Presentation/sorting SELECT REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path FROM dbo.Employees ORDER BY hid;   --------------------------------------------------------------------- -- Further Aspects of Working with HIERARCHYID ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Normalizing HIERARCHYID Values ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Stored Procedure: AddEmp, --   Inserts new employee who manages no one into the table --------------------------------------------------------------------- IF OBJECT_ID('dbo.AddEmp', 'P') IS NOT NULL   DROP PROC dbo.AddEmp; GO CREATE PROC dbo.AddEmp   @empid      AS INT,   @mgrid      AS INT,   @leftempid  AS INT,   @rightempid AS INT,    @empname    AS VARCHAR(25),   @salary     AS MONEY = 1000 AS   DECLARE @hid AS HIERARCHYID;   IF @mgrid IS NULL   SET @hid = hierarchyid::GetRoot(); ELSE   SET @hid = (SELECT hid FROM dbo.Employees WHERE empid = @mgrid).GetDescendant     ( (SELECT hid FROM dbo.Employees WHERE empid = @leftempid),       (SELECT hid FROM dbo.Employees WHERE empid = @rightempid) );   INSERT INTO dbo.Employees(empid, hid, empname, salary)   VALUES(@empid, @hid, @empname, @salary); GO   TRUNCATE TABLE dbo.Employees;   EXEC dbo.AddEmp @empid =  1, @mgrid = NULL, @leftempid = NULL, @rightempid = NULL, @empname = 'A'; EXEC dbo.AddEmp @empid =  2, @mgrid =    1, @leftempid = NULL, @rightempid = NULL, @empname = 'B'; EXEC dbo.AddEmp @empid =  3, @mgrid =    1, @leftempid =    2, @rightempid = NULL, @empname = 'C'; EXEC dbo.AddEmp @empid =  4, @mgrid =    1, @leftempid =    2, @rightempid =    3, @empname = 'D'; EXEC dbo.AddEmp @empid =  5, @mgrid =    1, @leftempid =    4, @rightempid =    3, @empname = 'E'; EXEC dbo.AddEmp @empid =  6, @mgrid =    1, @leftempid =    4, @rightempid =    5, @empname = 'F'; EXEC dbo.AddEmp @empid =  7, @mgrid =    1, @leftempid =    6, @rightempid =    5, @empname = 'G'; EXEC dbo.AddEmp @empid =  8, @mgrid =    1, @leftempid =    6, @rightempid =    7, @empname = 'H'; EXEC dbo.AddEmp @empid =  9, @mgrid =    8, @leftempid = NULL, @rightempid = NULL, @empname = 'I'; EXEC dbo.AddEmp @empid = 10, @mgrid =    8, @leftempid =    9, @rightempid = NULL, @empname = 'J'; EXEC dbo.AddEmp @empid = 11, @mgrid =    8, @leftempid =    9, @rightempid =   10, @empname = 'K'; EXEC dbo.AddEmp @empid = 12, @mgrid =    8, @leftempid =   11, @rightempid =   10, @empname = 'J'; EXEC dbo.AddEmp @empid = 13, @mgrid =    8, @leftempid =   11, @rightempid =   12, @empname = 'L'; EXEC dbo.AddEmp @empid = 14, @mgrid =    8, @leftempid =   13, @rightempid =   12, @empname = 'M'; EXEC dbo.AddEmp @empid = 15, @mgrid =    8, @leftempid =   13, @rightempid =   14, @empname = 'N'; EXEC dbo.AddEmp @empid = 16, @mgrid =    8, @leftempid =   15, @rightempid =   14, @empname = 'O'; EXEC dbo.AddEmp @empid = 17, @mgrid =    8, @leftempid =   15, @rightempid =   16, @empname = 'P'; EXEC dbo.AddEmp @empid = 18, @mgrid =    8, @leftempid =   17, @rightempid =   16, @empname = 'Q'; EXEC dbo.AddEmp @empid = 19, @mgrid =    8, @leftempid =   17, @rightempid =   18, @empname = 'E'; EXEC dbo.AddEmp @empid = 20, @mgrid =    8, @leftempid =   19, @rightempid =   18, @empname = 'S'; EXEC dbo.AddEmp @empid = 21, @mgrid =    8, @leftempid =   19, @rightempid =   20, @empname = 'T'; GO   SELECT * FROM dbo.Employees   -- Data before normalization SELECT   empid,   REPLICATE(' | ', lvl) + empname AS emp,   hid,   hid.ToString() AS path FROM dbo.Employees ORDER BY hid;   -- Normalize WITH EmpsRN AS (   SELECT     empid,     hid,     ROW_NUMBER() OVER(PARTITION BY hid.GetAncestor(1) ORDER BY hid) AS rownum   FROM dbo.Employees ), EmpPaths AS (   SELECT empid, hid, CAST('/' AS VARCHAR(900)) AS path   FROM dbo.Employees   WHERE hid = hierarchyid::GetRoot()       UNION ALL       SELECT C.empid, C.hid,     CAST(P.path + CAST(C.rownum AS VARCHAR(20)) + '/' AS VARCHAR(900))   FROM EmpPaths AS P     JOIN EmpsRN AS C       ON C.hid.GetAncestor(1) = P.hid ) UPDATE E   SET hid = CAST(EP.path AS HIERARCHYID) FROM dbo.Employees AS E   JOIN EmpPaths AS EP     ON E.empid = EP.empid;   -- Data after normalization SELECT   empid,   REPLICATE(' | ', lvl) + empname AS emp,   hid,   hid.ToString() AS path FROM dbo.Employees ORDER BY hid;   --------------------------------------------------------------------- -- Convert parent-child representation to new hierarchyid ---------------------------------------------------------------------   SET NOCOUNT ON; USE tempdb; GO IF OBJECT_ID('dbo.EmployeesOld') IS NOT NULL   DROP TABLE dbo.EmployeesOld; GO IF OBJECT_ID('dbo.EmployeesNew') IS NOT NULL   DROP TABLE dbo.EmployeesNew; GO CREATE TABLE dbo.EmployeesOld (   empid   INT          PRIMARY KEY,   mgrid   INT          NULL REFERENCES dbo.EmployeesOld,   empname VARCHAR(25)  NOT NULL,   salary  MONEY        NOT NULL ); CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.EmployeesOld(mgrid, empid);   INSERT INTO dbo.EmployeesOld(empid, mgrid, empname, salary) VALUES   (1,  NULL, 'David',  $10000.00),   (2,  1,    'Eitan',   $7000.00),   (3,  1,    'Ina',     $7500.00),   (4,  2,    'Seraph',  $5000.00),   (5,  2,    'Jiru',    $5500.00),   (6,  2,    'Steve',   $4500.00),   (7,  3,    'Aaron',   $5000.00),   (8,  5,    'Lilach',  $3500.00),   (9,  7,    'Rita',    $3000.00),   (10, 5,    'Sean',    $3000.00),   (11, 7,    'Gabriel', $3000.00),   (12, 9,    'Emilia' , $2000.00),   (13, 9,    'Michael', $2000.00),   (14, 9,    'Didi',    $1500.00); GO   CREATE TABLE dbo.EmployeesNew (   empid   INT NOT NULL PRIMARY KEY,   hid     HIERARCHYID NOT NULL,   lvl AS hid.GetLevel() PERSISTED,   empname VARCHAR(25) NOT NULL,   salary  MONEY       NOT NULL ); GO   WITH EmpsRN AS (   SELECT empid, mgrid, empname, salary,     ROW_NUMBER() OVER(PARTITION BY mgrid ORDER BY empid) AS rn   FROM dbo.EmployeesOld ), EmpPaths AS (   SELECT empid, mgrid, empname, salary,     CAST('/' AS VARCHAR(900)) AS cpath   FROM dbo.EmployeesOld   WHERE mgrid IS NULL       UNION ALL       SELECT C.empid, C.mgrid, C.empname, C.salary,     CAST(cpath + CAST(C.rn AS VARCHAR(20)) + '/' AS VARCHAR(900))   FROM EmpPaths AS P     JOIN EmpsRN AS C       ON C.mgrid = P.empid ) INSERT INTO dbo.EmployeesNew(empid, empname, salary, hid)   SELECT empid, empname, salary,     CAST(cpath AS HIERARCHYID) AS hid   FROM EmpPaths;     SELECT REPLICATE(' | ', lvl) + empname AS empname, hid.ToString() AS path FROM dbo.EmployeesNew ORDER BY hid;   --------------------------------------------------------------------- -- Sorting Separated Lists of Values ---------------------------------------------------------------------   USE tempdb; IF OBJECT_ID('dbo.IPs', 'U') IS NOT NULL DROP TABLE dbo.IPs;   -- Creation script for table IPs CREATE TABLE dbo.IPs (   ip varchar(15) NOT NULL,   CONSTRAINT PK_IPs PRIMARY KEY(ip),   -- CHECK constraint that validates IPs   CONSTRAINT CHK_IP_valid CHECK   (       -- 3 periods and no empty octets       ip LIKE '_%._%._%._%'     AND       -- not 4 periods or more       ip NOT LIKE '%.%.%.%.%'     AND       -- no characters other than digits and periods       ip NOT LIKE '%[^0-9.]%'     AND       -- not more than 3 digits per octet       ip NOT LIKE '%[0-9][0-9][0-9][0-9]%'     AND       -- NOT 300 - 999       ip NOT LIKE '%[3-9][0-9][0-9]%'     AND       -- NOT 260 - 299       ip NOT LIKE '%2[6-9][0-9]%'     AND       -- NOT 256 - 259       ip NOT LIKE '%25[6-9]%'   ) ); GO   -- Sample data INSERT INTO dbo.IPs(ip) VALUES   ('131.107.2.201'),   ('131.33.2.201'),   ('131.33.2.202'),   ('3.107.2.4'),   ('3.107.3.169'),   ('3.107.104.172'),   ('22.107.202.123'),   ('22.20.2.77'),   ('22.156.9.91'),   ('22.156.89.32');   -- IP Patterns IF OBJECT_ID('dbo.IPPatterns') IS NOT NULL DROP VIEW dbo.IPPatterns; GO CREATE VIEW dbo.IPPatterns AS   SELECT   REPLICATE('_', N1.n) + '.' + REPLICATE('_', N2.n) + '.'     + REPLICATE('_', N3.n) + '.' + REPLICATE('_', N4.n) AS pattern,   N1.n AS l1, N2.n AS l2, N3.n AS l3, N4.n AS l4,   1 AS s1, N1.n+2 AS s2, N1.n+N2.n+3 AS s3, N1.n+N2.n+N3.n+4 AS s4 FROM dbo.Nums AS N1, dbo.Nums AS N2, dbo.Nums AS N3, dbo.Nums AS N4 WHERE N1.n <= 3 AND N2.n <= 3 AND N3.n <= 3 AND N4.n <= 3; GO   -- Sort IPs, solution 1 SELECT ip FROM dbo.IPs   JOIN dbo.IPPatterns     ON ip LIKE pattern ORDER BY   CAST(SUBSTRING(ip, s1, l1) AS TINYINT),   CAST(SUBSTRING(ip, s2, l2) AS TINYINT),   CAST(SUBSTRING(ip, s3, l3) AS TINYINT),   CAST(SUBSTRING(ip, s4, l4) AS TINYINT);   -- Sort IPs, solution 2 SELECT ip FROM dbo.IPs ORDER BY CAST('/' + ip + '/' AS HIERARCHYID);   -- Generic form of problem SET NOCOUNT ON; USE tempdb; IF OBJECT_ID('dbo.T1', 'U') IS NOT NULL DROP TABLE dbo.T1;   CREATE TABLE dbo.T1 (   id  INT          NOT NULL IDENTITY PRIMARY KEY,   val VARCHAR(500) NOT NULL ); GO   INSERT INTO dbo.T1(val) VALUES   ('100'),   ('7,4,250'),   ('22,40,5,60,4,100,300,478,19710212'),   ('22,40,5,60,4,99,300,478,19710212'),   ('22,40,5,60,4,99,300,478,9999999'),   ('10,30,40,50,20,30,40'),   ('7,4,250'),   ('-1'),   ('-2'),   ('-11'),   ('-22'),   ('-123'),   ('-321'),   ('22,40,5,60,4,-100,300,478,19710212'),   ('22,40,5,60,4,-99,300,478,19710212');   SELECT id, val FROM dbo.T1 ORDER BY CAST('/' + REPLACE(val, ',', '/') + '/' AS HIERARCHYID);   --------------------------------------------------------------------- -- Nested Sets嵌套集合 ---------------------------------------------------------------------   --------------------------------------------------------------------- -- Assigning Left and Right Values 分配左值和右值 ---------------------------------------------------------------------   -- 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 = 1;   -- CTE with two numbers: 1 and 2 WITH TwoNums AS (   SELECT n FROM(VALUES(1),(2)) AS D(n) ), -- CTE with two binary sort paths for each node: --   One smaller than descendants sort paths --   One greater than descendants sort paths SortPath AS (   SELECT empid, 0 AS lvl, n,     CAST(n AS VARBINARY(MAX)) AS sort_path   FROM dbo.Employees CROSS JOIN TwoNums   WHERE empid = @root     UNION ALL     SELECT C.empid, P.lvl + 1, TN.n,     P.sort_path + 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 SortPath AS P     JOIN dbo.Employees AS C       ON P.n = 1       AND C.mgrid = P.empid     CROSS JOIN TwoNums AS TN ) SELECT * FROM SortPath ORDER BY sort_path; GO   -- CTE Code That Creates Nested Sets Relationships DECLARE @root AS INT = 1;   -- CTE with two numbers: 1 and 2 WITH TwoNums AS (   SELECT n FROM(VALUES(1),(2)) AS D(n) ), -- CTE with two binary sort paths for each node: --   One smaller than descendants sort paths --   One greater than descendants sort paths SortPath AS (   SELECT empid, 0 AS lvl, n,     CAST(n AS VARBINARY(MAX)) AS sort_path   FROM dbo.Employees CROSS JOIN TwoNums   WHERE empid = @root     UNION ALL     SELECT C.empid, P.lvl + 1, TN.n,     P.sort_path + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         -- *** determines order of siblings ***                         ORDER BY C.empname, C.empid, TN.n)       AS BINARY(4))   FROM SortPath AS P     JOIN dbo.Employees AS C       ON P.n = 1       AND C.mgrid = P.empid     CROSS JOIN TwoNums AS TN ), -- CTE with Row Numbers Representing sort_path Order Sort AS (   SELECT empid, lvl,     ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval   FROM SortPath ), -- CTE with Left and Right Values Representing -- Nested Sets Relationships NestedSets AS (   SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt   FROM Sort   GROUP BY empid, lvl ) SELECT * FROM NestedSets ORDER BY lft; GO   -- Materializing Nested Sets Relationships in a Table SET NOCOUNT ON; USE tempdb; GO   DECLARE @root AS INT = 1;   WITH TwoNums AS (   SELECT n FROM(VALUES(1),(2)) AS D(n) ), SortPath AS (   SELECT empid, 0 AS lvl, n,     CAST(n AS VARBINARY(MAX)) AS sort_path   FROM dbo.Employees CROSS JOIN TwoNums   WHERE empid = @root     UNION ALL     SELECT C.empid, P.lvl + 1, TN.n,     P.sort_path + CAST(       ROW_NUMBER() OVER(PARTITION BY C.mgrid                         -- *** determines order of siblings ***                         ORDER BY C.empname, C.empid, TN.n)       AS BINARY(4))   FROM SortPath AS P     JOIN dbo.Employees AS C       ON P.n = 1       AND C.mgrid = P.empid     CROSS JOIN TwoNums AS TN ), Sort AS (   SELECT empid, lvl,     ROW_NUMBER() OVER(ORDER BY sort_path) AS sortval   FROM SortPath ), NestedSets AS (   SELECT empid, lvl, MIN(sortval) AS lft, MAX(sortval) AS rgt   FROM Sort   GROUP BY empid, lvl ) SELECT E.empid, E.empname, E.salary, NS.lvl, NS.lft, NS.rgt INTO dbo.EmployeesNS FROM NestedSets 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 WHERE 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) ---------------------------------------------------------------------   -- 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 12-4: Creation Script for the BOMTC UDF IF OBJECT_ID('dbo.BOMTC') IS NOT NULL   DROP FUNCTION dbo.BOMTC; GO   CREATE FUNCTION 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 BOMTC UDF SELECT assemblyid, partid FROM BOMTC(); GO   -- 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;   -- 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 ---------------------------------------------------------------------   -- 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   -- Creation Script for the RoadsTC UDF IF OBJECT_ID('dbo.RoadsTC') IS NOT NULL   DROP FUNCTION dbo.RoadsTC; GO   CREATE FUNCTION dbo.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 RoadsTC UDF SELECT * FROM dbo.RoadsTC(); GO   -- 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;   -- 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   -- 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   -- Creation Script for the RoadsTC UDF IF OBJECT_ID('dbo.RoadsTC') IS NOT NULL   DROP FUNCTION dbo.RoadsTC; GO CREATE FUNCTION dbo.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.RoadsTC()) AS RTC WHERE rk = 1; GO   -- Cleanup DROP TABLE dbo.RoadPaths; GO