這裡是動態的拼接SQL code动态sql语句基本语法
1 :普通SQL语句可以用Exec执行 eg: Select * from tableName
Exec('select * from tableName')
Exec sp_executesql N'select * from tableName' -- 请注意字符串前一定要加N 2:字段名,表名,数据库名之类作为变量时,必须用动态SQL eg:
declare @fname varchar(20)
set @fname = 'FiledName'
Select @fname from tableName -- 错误,不会提示错误,但结果为固定值FiledName,并非所要。
Exec('select ' + @fname + ' from tableName') -- 请注意 加号前后的 单引号的边上加空格 当然将字符串改成变量的形式也可
declare @fname varchar(20)
set @fname = 'FiledName' --设置字段名 declare @s varchar(1000)
set @s = 'select ' + @fname + ' from tableName'
Exec(@s) -- 成功
exec sp_executesql @s -- 此句会报错 declare @s Nvarchar(1000) -- 注意此处改为nvarchar(1000)
set @s = 'select ' + @fname + ' from tableName'
Exec(@s) -- 成功
exec sp_executesql @s -- 此句正确 3. 输出参数
declare @num int,
@sqls nvarchar(4000)
set @sqls='select count(*) from tableName'
exec(@sqls)
--如何将exec执行结果放入变量中? declare @num int,
@sqls nvarchar(4000)
set @sqls='select @a=count(*) from tableName '
exec sp_executesql @sqls,N'@a int output',@num output
select @num
1 :普通SQL语句可以用Exec执行 eg: Select * from tableName
Exec('select * from tableName')
Exec sp_executesql N'select * from tableName' -- 请注意字符串前一定要加N 2:字段名,表名,数据库名之类作为变量时,必须用动态SQL eg:
declare @fname varchar(20)
set @fname = 'FiledName'
Select @fname from tableName -- 错误,不会提示错误,但结果为固定值FiledName,并非所要。
Exec('select ' + @fname + ' from tableName') -- 请注意 加号前后的 单引号的边上加空格 当然将字符串改成变量的形式也可
declare @fname varchar(20)
set @fname = 'FiledName' --设置字段名 declare @s varchar(1000)
set @s = 'select ' + @fname + ' from tableName'
Exec(@s) -- 成功
exec sp_executesql @s -- 此句会报错 declare @s Nvarchar(1000) -- 注意此处改为nvarchar(1000)
set @s = 'select ' + @fname + ' from tableName'
Exec(@s) -- 成功
exec sp_executesql @s -- 此句正确 3. 输出参数
declare @num int,
@sqls nvarchar(4000)
set @sqls='select count(*) from tableName'
exec(@sqls)
--如何将exec执行结果放入变量中? declare @num int,
@sqls nvarchar(4000)
set @sqls='select @a=count(*) from tableName '
exec sp_executesql @sqls,N'@a int output',@num output
select @num
(
ID INT,
CC VARCHAR(5),
VALUE INT
)
INSERT INTO A
SELECT 1, 'D ',100 UNION ALL
SELECT 2, 'D ',200 UNION ALL
SELECT 3, 'D ',300 UNION ALL
SELECT 1, 'E ',1000 UNION ALL
SELECT 2, 'E ',2000 UNION ALL
SELECT 3, 'E ',3000 UNION ALL
SELECT 1, 'F ',10 UNION ALL
SELECT 2, 'F ',20 UNION ALL
SELECT 3, 'F ',30
GO
DECLARE @S1 VARCHAR(100)
DECLARE @S VARCHAR(1000)
SET @S1= 'SELECT ID, '
SET @S= ' FROM (SELECT AA.ID, '
SELECT @S1=@S1+ 'MAX( '+CC+ ') '+CC+ ', '
,@S=@S+ 'CASE CC WHEN '''+CC+ ''' THEN (SELECT [VALUE] FROM A WHERE CC='''+CC+ ''' AND ID=AA.ID) ELSE 0 END AS '+CC+ ', ' FROM
(SELECT DISTINCT CC FROM A) B
SET @S=STUFF(@S1,LEN(@S1),1, ' ')+STUFF(@S,LEN(@S),1, ' ')+ ' FROM A AA) B GROUP BY B.ID '
EXEC(@S)
insert into tb values('张三' , '语文' , 74)
insert into tb values('张三' , '数学' , 83)
insert into tb values('张三' , '物理' , 93)
insert into tb values('李四' , '语文' , 74)
insert into tb values('李四' , '数学' , 84)
insert into tb values('李四' , '物理' , 94)
go--SQL SERVER 2000 静态SQL,指课程只有语文、数学、物理这三门课程。(以下同)
select 姓名 as 姓名 ,
max(case 课程 when '语文' then 分数 else 0 end) 语文,
max(case 课程 when '数学' then 分数 else 0 end) 数学,
max(case 课程 when '物理' then 分数 else 0 end) 物理
from tb
group by 姓名--SQL SERVER 2000 动态SQL,指课程不止语文、数学、物理这三门课程。(以下同)
declare @sql varchar(8000)
set @sql = 'select 姓名 '
select @sql = @sql + ' , max(case 课程 when ''' + 课程 + ''' then 分数 else 0 end) [' + 课程 + ']'
from (select distinct 课程 from tb) as a
set @sql = @sql + ' from tb group by 姓名'
exec(@sql) --SQL SERVER 2005 静态SQL。
select * from (select * from tb) a pivot (max(分数) for 课程 in (语文,数学,物理)) b--SQL SERVER 2005 动态SQL。
declare @sql varchar(8000)
select @sql = isnull(@sql + ',' , '') + 课程 from tb group by 课程
exec ('select * from (select * from tb) a pivot (max(分数) for 课程 in (' + @sql + ')) b')---------------------------------
http://topic.csdn.net/u/20080614/17/22e73f33-f071-46dc-b9bf-321204b1656f.html
等同于declare
@str varchar(2000)
set @str = 'select ID '
select @str = @str + ','+'max(case CC when '''+CC+''' then value else 0 end)'''+CC+''''
from (select distinct cc from A )b
select @str = @str +' from A group by ID'
exec (@str)
(
ID INT,
CC VARCHAR(5),
VALUE INT
)
INSERT INTO A
SELECT 1, 'D ',100 UNION ALL
SELECT 2, 'D ',200 UNION ALL
SELECT 3, 'D ',300 UNION ALL
SELECT 1, 'E ',1000 UNION ALL
SELECT 2, 'E ',2000 UNION ALL
SELECT 3, 'E ',3000 UNION ALL
SELECT 1, 'F ',10 UNION ALL
SELECT 2, 'F ',20 UNION ALL
SELECT 3, 'F ',30
GO
DECLARE @S1 VARCHAR(100)
DECLARE @S VARCHAR(1000)
--1
SET @S1= 'SELECT ID, '
SET @S= ' FROM (SELECT AA.ID, '
SELECT
@S1=@S1+ 'MAX( '+CC+ ') '+CC+ ', ',
@S=@S+ 'CASE CC WHEN '''+CC+ ''' THEN (SELECT [VALUE] FROM A WHERE CC= '''+CC+ ''' AND ID=AA.ID) ELSE 0 END AS '+CC+ ', '
FROM
(SELECT DISTINCT CC FROM A) B
SET @S=STUFF(@S1,LEN(@S1),1, ' ')+STUFF(@S,LEN(@S),1, ' ')+ ' FROM A AA) B GROUP BY B.ID '
exec(@S)
;
-- 2
set @s = null
select @s = isnull(@s+',','')+'['+cc+'] = sum(case when cc = '''+cc+''' then [value] end)'
from (SELECT DISTINCT CC FROM A) B
exec('select id,'+@s+' from a group by id')
drop table a
select @s = isnull(@s+',','')+'['+cc+'] = sum(case when cc = '''+cc+''' then [value] end)'
from (SELECT DISTINCT CC FROM A) B
exec('select id,'+@s+' from a group by id')
警告: 聚合或其它 SET 操作消除了空值。 麻烦各位帮看看
CREATE TABLE A
(
ID INT,
CC VARCHAR(5),
VALUE INT
)
INSERT INTO A
SELECT 1, 'D ',100 UNION ALL
SELECT 2, 'D ',200 UNION ALL
SELECT 3, 'D ',300 UNION ALL
SELECT 1, 'E ',1000 UNION ALL
SELECT 2, 'E ',2000 UNION ALL
SELECT 3, 'E ',3000 UNION ALL
SELECT 1, 'F ',10 UNION ALL
SELECT 2, 'F ',20 UNION ALL
SELECT 3, 'F ',30
GO DECLARE @S VARCHAR(1000) set @s = null
select @s = isnull(@s+',','')+'['+cc+'] = sum(case when cc = '''+cc+''' then [value] else 0 end)'
from (SELECT DISTINCT CC FROM A) B
exec('select id,'+@s+' from a group by id')
drop table a
/*
id D E F
----------- ----------- ----------- -----------
1 100 1000 10
2 200 2000 20
3 300 3000 30(3 行受影响)
*/