22,206
社区成员
发帖
与我相关
我的任务
分享
DECLARE @TB TABLE (id INT,name varchar(10))
INSERT @TB
SELECT 1 ,'jack' UNION ALL
SELECT 2 ,'sam' UNION ALL
SELECT 6 ,'micle' UNION ALL
SELECT 7 ,'Jop' UNION ALL
SELECT 7 ,'Jop' UNION ALL
SELECT 12, 'Nill'
DECLARE @s1 varchar(10),@s2 varchar(20)
--SQL 1
SELECT @s1='10_'
SELECT @s1=@s1+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
SELECT @s1
--SQL 2(此处语句和1中一样,只是变量@s2的长度比@s1大,结果就完全不一样了)
SELECT @s2='20_'
SELECT @s2=@s2+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
SELECT @s2
--SQL 3(如果把两个变量放在一起,那么结果就一样了)
SELECT @s1='10_',@s2='20_'
SELECT @s1=@s1+NAME,@s2=@s2+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
SELECT @s1,@s2
DECLARE @TB TABLE (id INT,name varchar(10))
INSERT @TB
SELECT 1 ,'jack' UNION ALL
SELECT 2 ,'sam' UNION ALL
SELECT 6 ,'micle' UNION ALL
SELECT 7 ,'Jop' UNION ALL
SELECT 7 ,'Jop' UNION ALL
SELECT 12, 'Nill'
DECLARE @s1 varchar(10),@s2 varchar(20)
--SQL 1
SELECT @s1='10_'
SELECT @s1=@s1+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
(所影响的行数为 2 行)
StmtText
------------------------------------------------------------------------
|--Sort(ORDER BY:(@TB.[id] DESC))
|--Compute Scalar(DEFINE:([Expr1002]=Convert([@s1]+@TB.[name])))
|--Sort(TOP 2, ORDER BY:(@TB.[id] ASC))
|--Table Scan(OBJECT:(@TB))
StmtText
-------------------------------------------------------------
SELECT @s1
SELECT @s2=@s2+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
(所影响的行数为 2 行)
StmtText
-------------------------------------------------------------------
|--Compute Scalar(DEFINE:([Expr1002]=Convert([@s2]+@TB.[name])))
|--Sort(ORDER BY:(@TB.[id] DESC))
|--Sort(TOP 2, ORDER BY:(@TB.[id] ASC))
|--Table Scan(OBJECT:(@TB))
SELECT @s1='10_',@s2='20_'
SELECT @s1=@s1+NAME,@s2=@s2+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
StmtText
---------------------------------------------------------------------------------------------------------
|--Compute Scalar(DEFINE:([Expr1002]=Convert([@s1]+@TB.[name]), [Expr1003]=Convert([@s2]+@TB.[name])))
|--Sort(ORDER BY:(@TB.[id] DESC))
|--Sort(TOP 2, ORDER BY:(@TB.[id] ASC))
|--Table Scan(OBJECT:(@TB))
DECLARE @s1 varchar(10)
SELECT @s1='10_'
SELECT @s1=@s1+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID DESC
) a
ORDER BY ID DESC
SELECT @s1
SELECT @s1='10_'
SELECT @s1=@s1+NAME
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
SELECT @s1
/*
@s1 中 把查询语句 最后面的排序去掉的话 就全部显示了 只是顺序不对
为什么呢?? 排序就显示不全,不排序就全部显示
*/
DECLARE @s1 varchar(12)
--SQL 1
SELECT @s1='10_'
SELECT @s1 = @s1 + name
FROM
(
SELECT TOP 2 id,name FROM @TB ORDER BY ID
) a
ORDER BY ID DESC
SELECT @s1
SELECT LEN(@s1)
create table tb(姓名 varchar(10) , 课程 varchar(10) , 分数 int)
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 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)