while循环中的表变量并非每次都初始化:SQL Server [英] Table variables inside while loop not initializing everytime : SQL Server

问题描述

我想知道为什么while循环中的表变量的行为不像其他变量.表变量仅创建一次，并将在整个循环中使用.但每次循环增加时，其他变量都会初始化.

I am wondering why the table variables inside while loop does not behave like other variables. Table variables created only once and will be used across through out whole looping. but other variables getting initialized every time when loop increases.

查看下面的代码以获取更多信息

Check out the below code for more info

declare @tt int
set @tt =10
while @tt>0
begin

        declare @temptable table(id int identity(1,1),sid bigint)
        insert into @temptable 
                select @tt union all
                select @tt + 1 

                select * from @temptable 
               --delete from @temptable
                set @tt=@tt-1
end

这是一个错误吗?

推荐答案

您的前提是错误的.每次遇到声明语句时，其他变量也不会重新初始化.

Your premise is wrong. Other variables don't get reinitialised every time the declare statement is encountered either.

set nocount on

declare @tt int
set @tt =10
while @tt>0
begin

        declare @i int

        set @i = isnull(@i,0) + 1
        print @i
        set @tt=@tt-1

end

打印

1
2
...
9
10

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