求动态SQL语句

[zoulipeng]

--此动态SQL,怎么写？

declare @tablename varchar(20)
set @tableName='yourtablename'

if exists (select * from sysobjects where name = 'yourtablename')
drop table @tableName
go
CREATE TABLE @tableName (CALLIDX BIGINT,AIIDX BIGINT)


如何执行?

[520zyb]

EXEC('drop table '+@tableName)

[520zyb]

EXEC('CREATE TABLE '+@tableName+' (CALLIDX BIGINT,AIIDX BIGINT)')
中间不能加GO

[OracleRoob]

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

[子陌红尘]

declare @tablename varchar(20)
set @tableName='yourtablename'

if exists (select * from sysobjects where name = @tableName)
exec('drop table '+@tableName)
go

exec('CREATE TABLE '+@tableName+'(CALLIDX BIGINT,AIIDX BIGINT)')

[zlp321002]

--try
declare @tablename varchar(20),@s varchar(8000)
set @tablename='yourtablename'
set @s=' if exists (select * from sysobjects where xtype=''u'' and status>=0 and name = '''+@tablename+''')'+char(13)
set @s=@s+' drop table '+@tablename+' '+char(13)
set @s=@s+' CREATE TABLE '+@tablename+'(CALLIDX BIGINT,AIIDX BIGINT)'
exec(@s)