检查存储过程中参数是否为空或为空 [英] Check if a parameter is null or empty in a stored procedure

问题描述

我知道如何检查参数是否为空，但是我不确定如何检查其是否为空...我有这些参数，我想检查先前的参数为空还是为空，然后像下面那样设置它们

I know how to check if a parameter is null but i am not sure how to check if its empty ... I have these parameters and I want to check the previous parameters are empty or null and then set them like below

ALTER PROCEDURE [dbo].[GetSummary]
    @PreviousStartDate NVARCHAR(50) ,
    @PreviousEndDate NVARCHAR(50) ,
    @CurrentStartDate NVARCHAR(50) ,
    @CurrentEndDate NVARCHAR(50)
AS
  BEGIN
    IF(@PreviousStartDate IS NULL OR EMPTY)
        SET @PreviousStartdate = '01/01/2010'  for example..

我将很感谢您的帮助.

推荐答案

我有时会使用 NULLIF 就像这样...

I sometimes use NULLIF like so...

IF NULLIF(@PreviousStartDate, '') IS NULL

可能没有理由比@Oded和@bluefeet所建议的方式更好，只是风格上的偏爱.

There's probably no reason it's better than the way suggested by @Oded and @bluefeet, just stylistic preference.

@danihp的方法确实很酷，但是当我以为空或空的时候，我疲倦的老大脑就不会灰飞烟灭了:-)

@danihp's method is really cool but my tired old brain wouldn't go to COALESCE when I'm thinking is null or empty :-)

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