SQL动态执行的语法实例

转载地址：http://www.cnblogs.com/yinhaiming/articles/1403888.html

动态语句语法（太有用了）:

--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

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)