select top 后面不能跟变量吗？
需求：
实现一个简单的分页存储过程。不使用通用存储过程，不到万不得已不使用存储过程内的字符串拼接。
实现：
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
CREATE PROCEDURE [dbo].[sp_QueryPage_User]
@Page int = 1,
@PageSize int = 10
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
select top @PageSize * from tbl_User
where (UserNativeId not in (select top @Page*@PageSize UserNativeId from tbl_User order by UserNativeId))
order by UserNativeId
END
go
错误提示：
Msg 102, Level 15, State 1, Procedure sp_QueryPage_User, Line 15
Incorrect syntax near '@PageSize '.
Msg 102, Level 15, State 1, Procedure sp_QueryPage_User, Line 16
Incorrect syntax near '@Page '.
分析： 将变量替换为常量后可以通过
例如将
select top @PageSize * from tbl_User
where (UserNativeId not in (select top @Page*@PageSize UserNativeId from tbl_User order by UserNativeId))
order by UserNativeId
替换为
select top 10 * from tbl_User
where (UserNativeId not in (select top 30 UserNativeId from tbl_User order by UserNativeId))
order by UserNativeId
求解： select top 后面不能跟变量？还是有什么别的语法可以通过的？
[解决办法]
declare @int int
set @int =1
exec( 'select top '+@int+ ' form sysobjects ')
[解决办法]
CREATE PROCEDURE [dbo].[sp_QueryPage_User]
@Page int = 1,
@PageSize int = 10
AS
declare @sql varchar(1000)
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
set @sql= '
select top '+@PageSize+ ' * from tbl_User
where (UserNativeId not in (select top '+@Page*@PageSize+ ' UserNativeId from tbl_User order by UserNativeId))
order by UserNativeId '
exec(@sql)
END
go
[解决办法]
declare @num int
select @num = 10
exec( 'select top '+@num+ ' * from sysobjects ')
[解决办法]
用动态SQL语句。
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
[解决办法]
用动态SQL语句。
[解决办法]
sql 2005支持.
如果你用sql 2005, 那可以写:
select top (变量或者表达式) * from tb
delete top (变量或者表达式) tb
