如下代码所示
declare @ID int
declare @sql nvarchar(1000)
set @sql='select @ID=id from tb_user'
exec sp_executesql @sql,N'@ID as int',@ID
print @ID
以上代码查询不到任何结果,也不能输出任何数字但是
把 set @sql='select @ID=id from tb_user'中的 @ID= 去掉
改为
exec sp_executesql @sql,N'@ID as int',@ID
就能查询到结果了(当然,@ID的值无法得到正确结果)请问下为什么呢
declare @ID int
declare @sql nvarchar(1000)
set @sql='select @ID=id from tb_user'
exec sp_executesql @sql,N'@ID as int',@ID
print @ID
以上代码查询不到任何结果,也不能输出任何数字但是
把 set @sql='select @ID=id from tb_user'中的 @ID= 去掉
改为
exec sp_executesql @sql,N'@ID as int',@ID
就能查询到结果了(当然,@ID的值无法得到正确结果)请问下为什么呢
declare @sql nvarchar(1000)
set @sql='select @ID=id from tb_user'
exec sp_executesql @sql,N'@ID as int output',@ID output
select @ID--动态语句语法
/******************************************************************************************************************************************************
动态语句语法:exec\sp_executesql语法整理人:中国风(Roy)日期:2008.06.06
******************************************************************************************************************************************************/
--动态语句语法:--方法1查询表改为动态
select * from sysobjects
exec('select ID,Name from sysobjects')
exec sp_executesql N'select ID,Name from sysobjects'--多了一个N为unicode--方法2:字段名,表名,数据库名之类作为变量时,用动态SQL
declare @FName varchar(20)
set @FName='ID'
exec('select '+@FName+' from sysobjects where '+@FName+'=5' )
declare @s varchar(1000)
set @s=N'select '+@FName+' from sysobjects where '+@FName+'=5'
exec sp_executesql @s--会报错
declare @s nvarchar(1000)--改为nvarchar
declare @FName varchar(20)
set @FName='ID'
set @s=N'select '+@FName+' from sysobjects where '+@FName+'=5'
exec sp_executesql @s--成功
--方法3:输入参数declare @i int,@s nvarchar(1000)
set @i=5
exec('select ID,Name from sysobjects where ID='+@i)set @s='select ID,Name from sysobjects where ID=@i'
exec sp_executesql @s,N'@i int',@i--此处输入参数要加上N--方法4:输出参数declare @i int,@s nvarchar(1000)
set @s='select @i=count(1) from sysobjects'--用exec
exec('declare @i int '+@s+' select @i')--把整个语句用字符串加起来执行--用sp_executesql
exec sp_executesql @s,N'@i int output',@i output--此处输出参数要加上N
select @i
--方法5:输入输出--用sp_executesql
declare @i int,@con int,@s nvarchar(1000)
set @i=5
select @s='select @con=count(1) from sysobjects where ID>@i'
exec sp_executesql @s,N'@con int output,@i int',@con output ,@i
select @con--用exec
declare @i int,@s nvarchar(1000)
set @i=5
select @s='declare @con int select @con=count(1) from sysobjects where ID>'+rtrim(@i)+' select @con'
exec(@s)
declare @custid nchar(5),@sql nvarchar(100)
set @custid='VINET'
set @sql='select * from orders where customerid='''+@custid+''''
exec(@sql)
--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