CREATE PROCEDURE dbo.Dlookup
@tablename sysname(128),
@field varchar(50),
@swhere varchar
AS
exec('select '+@field+' from (select name from sysobjects where name='''+@tablename+''') where '+@swhere)
GO
@tablename sysname(128),
@field varchar(50),
@swhere varchar
AS
exec('select '+@field+' from (select name from sysobjects where name='''+@tablename+''') where '+@swhere)
GO
@tablename sysname(128),
@field varchar(50),
@swhere varchar(1000) --注意,不指定varchar变量的长度,默认为varchar(1)
AS
exec('select '+@field+' from (select name from sysobjects where name='''+@tablename+''') where '+@swhere)
GO
@tablename sysname(128),
@field varchar(50),
@swhere varchar(1000)
ASexec('select ' + @field + ' from (select name from sysobjects where name=''' + @tablename + ''') where ' + @swhere)
go
--1、参数类型,如果不指定varchar变量的长度,默认为varchar(1)
--2、动态SQL中的单引号两个表示一个
--3、这样的业务要求需要使用动态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
@tablename sysname, -- sysname不能指定长度
@field varchar(50),
@swhere varchar(1000) --注意,不指定varchar变量的长度,默认为varchar(1)
AS
exec('select '+@field+' from (select name from sysobjects where name='''+@tablename+''') as t where '+@swhere)
GOexec Dlookup 't1','name',' name=''t1'''
godrop procedure Dlookup或者
CREATE PROCEDURE Dlookup
@tablename sysname,
@field varchar(50),
@swhere varchar(1000) --注意,不指定varchar变量的长度,默认为varchar(1)
AS
BEGIN
declare @sql nvarchar(4000)
set @sql=N'select '+@field+' from (select name from sysobjects where name=@tablename) as t where '+@swhere
print @sql
exec sp_executesql @sql,N'@tablename sysname',@tablename
END
GOexec Dlookup 't1','name',' name=''t1'''
godrop procedure Dlookup