下面语句是非法的:
DECLARE @TABLENAME VARCHAR(20)
DECLARE @QCSL DECIMAL(16,2)
SELECT @QCSL = SL FROM @TABLENAME 如何能实现我想要的@QCSL的值?
DECLARE @TABLENAME VARCHAR(20)
DECLARE @QCSL DECIMAL(16,2)
SELECT @QCSL = SL FROM @TABLENAME 如何能实现我想要的@QCSL的值?
DECLARE @QCSL DECIMAL(16,2) declare @SQL nvarchar(1000)
set @SQL = 'SELECT @QCSL = SL FROM '+@TABLENAMEexec sp_executesql @SQL, N'@QCSL DECIMAL(16,2) output', @QCSL output
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
declare @TABLENAME table (sl numeric(18,2),s2 int)
insert into @TABLENAME select 10,10
select @QCSL=sl from @TABLENAME
select @QCSL
/*
10.00
*/