Does GetDate() get re-evaluated for each iteration within loop within a transaction?

问题

I have a scenario where I am looping through a resultset within a transaction and I need to INSERT a unique datetime value within a table for each iteration through the resultset - will GetDate() be recalculated each time or will it only be calculated the first time and then be the same for each iteration through the loop?

My pseudo-code is below:

BEGIN TRANSACTION
GO

DECLARE @ID INT 
DECLARE @table TABLE (/* Columns */) 

WHILE (SELECT COUNT(*) FROM @table WHERE PROCESSED = 0) > 0
      BEGIN

            SELECT TOP 1 @ID = ID FROM @table WHERE PROCESSED = 0 

            -- INSERT GetDate() into child table at this point. 
            -- Will GetDate() be re-evaluated each time? 

            UPDATE @table SET PROCESSED = 1 WHERE ID = @ID 

      END

END TRANSACTION
GO

Thanks in advance!

回答1:

Yes.

If you want to avoid re-evaluating it, store its value in a variable before the loop, and insert that instead.

来源：https://stackoverflow.com/questions/1847720/does-getdate-get-re-evaluated-for-each-iteration-within-loop-within-a-transact