DB2的一些常用SQL写法(转)

转自：http://hi.baidu.com/emilypear/blog/item/6bd1b399bedacf0b6f068cb0.html

-- 创建一个自定义单值类型
create   distinct type var_newtype
as decimal(5,2) with comparisons;

-- var_newtype 类型名
-- decimal(5,2) 实际的类型

-- 删除一个自定义单值类型
drop distinct type var_newtype;

-- 创建一个自定义结构数据类型
create type my_type as(
username varchar(20),
department integer,
salary decimal(10,2))
not final
mode db2sql;

-- 修改自定义结构数据类型,我目前还没有发现删除属性的方法.
alter type my_type
add attribute hiredate date;

-- 删除自定义结构数据类型
drop type my_type;

-- 获取系统当前日期
select current date from sysibm.sysdummy1;
select current time from sysibm.sysdummy1;
select current timestamp from sysibm.sysdummy1;

--sysibm.sysdummy1表是一个特殊的内存中的表，用它可以发现如上面演示的 DB2 寄存器的值。您也可以使用关键字 VALUES 来对寄存器或表达式求值。
VALUES current date;
VALUES current time;
VALUES current timestamp;

-- VALUES的更多用法

VALUES 2+5;

VALUES 'hello lavasoft!';

values 56
union all
values 45;

values 1,2,3,4,5,6
union all
values 7,8,9,10,11,12
order by 1;

-- 更多变态级DB2 SQL写法,AnyOneTable表示任意一个存在的表

select 234 from AnyOneTable;
select distinct 234 from AnyOneTable;
select distinct 234 as 1 from AnyOneTable;

select 'DB2变态级的SQL哈哈' from AnyOneTable;
select distinct 'DB2变态级的SQL哈哈' from AnyOneTable;
select distinct 'DB2变态级的SQL哈哈' as 1 from AnyOneTable;

     --(嘿嘿,好玩吧,你可以用任意一个表来当sysibm.sysdummy1用.不过不推荐这么做,除非你不记得sysibm.sysdummy1怎么写了,Oracle中(对应dual)也一样!哈哈哈哈!)

-- 定义变量,还可以设定默认值,给变量赋值
declare var1 char(2);
declare var2 int default 0;

set var1 = 'aa';
set var2 =23;

--创建一个动态游标变量
declare d_cur integer;

-- 给变量赋值的另一种方法
values expr1, expr2, expr3 into a, b, c;
-- 相当于
set a = expr1;
set b = expr2;
set c = expr3;

-- 还有一种赋值方式

set prodname = (case
                   when (name is not null) then name
                   when (namestr is not null) then namestr
                   else   defaultname
                 end);
-- 相当于
set prodname = coalesce(name, namestr, defaultname);
--这个类似oracle的decode()和nvl()函数的合并.

-- 定义一个游标
declare cur1 cursor with return to client for select * from dm_hy;
declare cur2 cursor for select * from dm_hy; -- 静态游标

-- 创建数据表,并添加注释,插入数据.
CREATE TABLE tbr_catalog (
   id bigint   not null   generated by default as identity,
   type smallint not null,
   name varchar(255),
   parentid bigint,
   cataloglevel bigint,
   description varchar(255),
   PRIMARY KEY   (id)
);
comment on table tbr_catalog is 'Birt报表目录表';
comment on column tbr_catalog.ID is '标识';
comment on column tbr_catalog.type is '目录类型';
comment on column tbr_catalog.name is '目录名称';
comment on column tbr_catalog.parentid is '目录父标识';
comment on column tbr_catalog.cataloglevel is '目录层次';
comment on column tbr_catalog.description is '目录描述';

-- 给数据表插入数据
insert into tbr_catalog(id, type, name, parentid, cataloglevel, description)
values (1, 0, '系统报表', 0, 0, '');
insert into tbr_catalog(id, type, name, parentid, cataloglevel, description)
values (2, 1, '用户报表', 0, 0, '');

-- 创建外键
alter table tbr_storage
add constraint fk_tbr_storage
foreign key (catalogid)
references tbr_catalog(id);

-- 更改表,添加列
alter table aaa add sex varchar(1);

-- 更改表,删除列
alter table aaa drop column sex;

-- 去掉参数前后的空格
rtrim(dm_hy.mc);

-- 定义临时表,通过已有person表来创建
declare global temporary table gbl_temp
like person
on commit delete rows --提交时删除数据
not logged -- 不在日志中纪录
in usr_tbsp -- 选用表空间
-- 此语句创建一个名为 gbl_temp 的用户临时表。定义此用户临时表 所使用的列的名称和说明与 person 的列的名称和说明完全相同。

-- 创建有两个字段的临时表  
     -- 定义一个全局临时表tmp_hy
declare global temporary table session.tmp_hy
     (
        dm varchar(10),
        mc varchar(10)         
     )
      with replace -- 如果存在此临时表，则替换
      not logged;   -- 不在日志里纪录

     -- 给临时表插入三条数据
     insert into session.tmp_hy values('1','1');
     insert into session.tmp_hy values('1','1');
     insert into session.tmp_hy values('1','1');

-- 通过查询批量插入数据

inster into tab_bk(select code,name from table book);

-- select ... into的用法

select * into :h1, :h2, :h3, :h4
      from emp
      where empno = '528671';

-- 语句的流程控制

if() then
open cur1
fetch cur1 into t_equipid;
while(at_end<>1)do
   ......
set t_temp=0;                                                            
end while;
close cur1;
else
......
end if;

-- 外连接

select empno,deptname,projname
   from (emplyoee
   left outer join project
   on respemp=empon)
   left outer join department
   on mgrno=empno;

-- in、like、order by(... ASC|DESC)的用法
select * from book t
where t.name like '%J_编程%'
and t.code in（'J565333','J565222');

order by t.name asc

-- 汇总表(概念复杂，难以理解，不常用）
create summary table sumy_stable1
   as (select workdept,
     count(*) as reccount,
     sum(salary) as salary,
     sum(bonus) as bonus
   from employee group by workdept)
data initially deferred
refresh immediate;

-- 使用SQL一次处理一个集合语义
-- （优化前） select语句中每行的过程层和数据流层之间都有一个上下文切换
declare cur1 cursor for col1,col2 from tab_comp;
open cur1;
fetch cur1 into v1,v2;
while SQLCODE<> 100 do
if (v1>20) then
   insert into tab_sel values(20,v1);
else
   insert into tab_sel values(v1,v2);
end if;
fetch cur1 into v1,v2;
end while;

-- （优化后）没有过程层和数据流层之间的上下文切换
declare cur1 cursor for col1,col2 from tab_comp;
open cur1;
fetch cur1 into v1,v2;
while SQLCODE<> 100 do
insert into tab_sel(select (case
          when col1>20 then 20
             else col1
         end),
         col2
       from tab_comp);
fetch cur1 into v1,v2;
end while;

-- DB2函数分三类：列函数、标量函数、表函数
-- 列函数输入一组数据，输出单一结果。
-- 标量函数接收一个值，返回另外一个值。
-- 表函数只能用于SQL语句的from字句中，它返回一个表的列，类似于一个已创建的常规表。

-- 下面是个标量函数的例子。
create function (salary int,bonus_percent int)
returns int
language SQL contains SQL
return(
salary * bonus_percent/100
)

-- 下面是表函数
create function get_marks(begin_range int,end_range int)
returns table(cid candidate_id,
        number test_id,
        score score)
language SQL reads SQL DATA
return
     select cid,number,score
     from test_taken
     where salary between (begin_range) and score(end_range)

example 1: define a scalar function that returns the tangent of a value using the existing sine and cosine functions.

    create function tan (x double)
      returns double
      language sql
      contains sql
      no external action
      deterministic
      return sin(x)/cos(x)               

example 2: define a transform function for the structured type person.

     
    create function fromperson (p person)
      returns row (name varchar(10), firstname varchar(10))
      language sql
      contains sql
      no external action
      deterministic
      return values (p..name, p..firstname)

example 3: define a table function that returns the employees in a specified department number.

     
    create function deptemployees (deptno char(3))
      returns table (empno char(6),
                     lastname varchar(15),
                     firstname varchar(12))
      language sql
      reads sql data
      no external action
      deterministic
      return
        select empno, lastname, firstnme
          from employee
          where employee.workdept = deptemployees.deptno

example 4: define a scalar function that reverses a string.

    create function reverse(instr varchar(4000))
      returns varchar(4000)
      deterministic no external action contains sql
      begin atomic
      declare revstr, reststr varchar(4000) default '';
      declare len int;
      if instr is null then
      return null;
      end if;
      set (reststr, len) = (instr, length(instr));
      while len > 0 do
      set (revstr, reststr, len)
        = (substr(reststr, 1, 1) concat revstr,
        substr(reststr, 2, len - 1),
        len - 1);
      end while;
      return revstr;
    end

example 4: define the table function from example 4 with auditing.

    create function deptemployees (deptno char(3))
      returns table (empno char(6),
                     lastname varchar(15),
                     firstname varchar(12))
      language sql
      modifies sql data
      no external action
      deterministic
      begin atomic
        insert into audit
        values (user,
                'table: employee prd: deptno = ' concat deptno);
        return
          select empno, lastname, firstnme
            from employee
            where employee.workdept = deptemployees.deptno
      end

-- for循环语句的用法

begin atomic
declare fullname char(40);
for vl as
    select firstnme, midinit, lastname from employee
   do
   set fullname = lastname concat ','
     concat firstnme concat ' ' concat midinit;
   insert into tnames values (fullname);
end for
end

-- leave的用法

create procedure leave_loop(out counter integer)
language sql
begin
    declare v_counter integer;
    declare v_firstnme varchar(12);
    declare v_midinit char(1);
    declare v_lastname varchar(15);
    declare at_end smallint default 0;
    declare not_found condition for sqlstate '02000';
    declare c1 cursor for
   select firstnme, midinit, lastname
     from employee;
    declare continue handler for not_found
   set at_end = 1;
    set v_counter = 0;
    open c1;
    fetch_loop:
    loop
   fetch c1 into v_firstnme, v_midinit, v_lastname;
   if at_end <> 0 then leave fetch_loop;
   end if;
   set v_counter = v_counter + 1;
    end loop fetch_loop;
    set counter = v_counter;
    close c1;
end

-- if语句的用法

    create procedure update_salary_if
      (in employee_number char(6), inout rating smallint)
      language sql
      begin
        declare not_found condition for sqlstate '02000';
        declare exit handler for not_found
          set rating = -1;
        if rating = 1
          then update employee
          set salary = salary * 1.10, bonus = 1000
          where empno = employee_number;
        elseif rating = 2
          then update employee
          set salary = salary * 1.05, bonus = 500
          where empno = employee_number;
        else update employee
          set salary = salary * 1.03, bonus = 0
          where empno = employee_number;
        end if;
      end

-- loop的用法

    create procedure loop_until_space(out counter integer)
      language sql
      begin
        declare v_counter integer default 0;
        declare v_firstnme varchar(12);
        declare v_midinit char(1);
        declare v_lastname varchar(15);
        declare c1 cursor for
          select firstnme, midinit, lastname
            from employee;
        declare continue handler for not found
          set counter = -1;
        open c1;
        fetch_loop:
        loop
          fetch c1 into v_firstnme, v_midinit, v_lastname;
          if v_midinit = ' ' then
            leave fetch_loop;
          end if;
          set v_counter = v_counter + 1;
        end loop fetch_loop;
        set counter = v_counter;
        close c1;
      end

-- return的用法

    begin
    ...
      goto fail
    ...
      success: return 0
      fail: return -200
    end