如何组织无限while循环在SQL Server？ [英] How to organize infinite while loop in SQL Server?

问题描述

我要使用无限 WHILE 循环在SQL Server 2005，并使用 BREAK 关键字从中退出某些状态。

I want to use infinite WHILE loop in SQL Server 2005 and use BREAK keyword to exit from it on certain condition.

，而真不工作，所以我必须使用，而1 = 1 。
有没有更好的方式来组织无限循环？

while true does not work, so I have to use while 1=1. Is there a better way to organize infinite loop ?

我知道，我可以使用转到，但，而1 = 1开始...结束看起来更好结构

I know that I can use goto, but while 1=1 begin ... end looks better structurally.

推荐答案

在除 WHILE 1 = 1 作为其他答案建议，我常常添加一个超时发送我的SQLinfintie循环，如下面的示例：

In addition to the WHILE 1 = 1 as the other answers suggest, I often add a "timeout" to my SQL "infintie" loops, as in the following example:

DECLARE @startTime datetime2(0) = GETDATE();

-- This will loop until BREAK is called, or until a timeout of 45 seconds.
WHILE (GETDATE() < DATEADD(SECOND, 45, @startTime))
BEGIN
    -- Logic goes here: The loop can be broken with the BREAK command.

    -- Throttle the loop for 2 seconds.    
    WAITFOR DELAY '00:00:02';
END

我发现了一个存储过程中有用的上述技术，被从长轮询AJAX 后端。其在数据库方面的循环不必不断袭来数据库来检查新的数据释放申请。

I found the above technique useful within a stored procedure that gets called from a long polling AJAX backend. Having the loop on the database-side frees the application from having to constantly hit the database to check for fresh data.

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