SQL Server对select语句返回多条记录给变量赋值时的处理情况

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