大考验:测试SQLServer各个版本的性能

核心提示： declare @user nvarchar(20) select @user='user1' use countme /*判断用户是否存在*/ declare @userweek int select @userweek=[week] from base where userid=@user sel

　　declare @user nvarchar(20)

select @user='user1'

use countme

/*判断用户是否存在*/

declare @userweek int

select @userweek=[week] from base where userid=@user

select @@rowcount

if @@rowcount=0

return

select @userweek



最后的@userweek打印出来的结果就是记录用户名为user1的week字段的值



而当我们用下面的语句选择所有记录时(没有where限制)

declare @user nvarchar(20)

select @user='user1'

use countme

/*判断用户是否存在*/

declare @userweek int

select @userweek=[week] from base

select @@rowcount

if @@rowcount=0

return

select @userweek



最后@userweek打印出来的值是返回的所有记录中排名最后一条记录的week字段值