如何检查字段是否为空或空的mysql? [英] How to check if field is null or empty mysql?

问题描述

我试图弄清楚如何检查一个字段是否为空或为空.我有这个

I am trying to figure out how to check if a field is null or empty. I have this

SELECT IFNULL(field1, 'empty') as field1 from tablename

我需要添加一张额外的支票field1 != ""之类的

I need to add an additional check field1 != "" something like

SELECT IFNULL(field1, 'empty') OR field1 != ""  as field1 from tablename

有什么想法要实现吗?

推荐答案

可以使用

SELECT IF(field1 IS NULL or field1 = '', 'empty', field1) as field1 
from tablename

或

SELECT case when field1 IS NULL or field1 = ''
            then 'empty'
            else field1
       end as field1 
from tablename

如果只想检查null而不是空字符串，则也可以使用ifnull()或coalesce(field1, 'empty').但这不适用于空字符串.

If you only want to check for null and not for empty strings then you can also use ifnull() or coalesce(field1, 'empty'). But that is not suitable for empty strings.

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