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declare @totalCounts int
................
set @sql =N'select '+str(@totalCounts)+'=count(*) from '+@tblname
exec sp_executesql @sql,N'@totalcounts int output',@totalcounts output
select @totalcounts
declare @num int, @sqls nvarchar(4000)
set @sqls='select @a=count(*) from authors '
exec sp_executesql @sqls,N'@a int output',@num output
select 'sql server 2000 自带示例库pubs的表ahthors的行数 = ' + cast(@num as varchar)
/*
sql server 2000 自带示例库pubs的表ahthors的行数 = 23
(所影响的行数为 1 行)
*/
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
--最后一段.
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
create table tb(id int,name varchar(20))
insert into tb select 1,'小磊'
declare @JobEnd varchar(50) ,@id int,@sql nvarchar(4000)
set @id=1
set @sql='select @JobEnd=name from tb where id='+ltrim(@id)
exec sp_executesql @sql,N'@JobEnd varchar(50) output',@JobEnd output
print @JobEnd
declare @sql nvarchar(4000)
declare @totalCounts int
set @sql =N'select @cnt=count(*) from '+@tblname
exec sp_executesql @sql,N'@cnt int output',@totalCounts output
select @totalcounts