mysql返回非空字段

这两者都适用 null 值以及空字符串( '' )

SELECT IF(LENGTH(firstname), firstname, lastname) as name from users;

在MySQL中有几种方法可以做到这一点。

你可以使用 coalesce() 函数的参数中返回第一个非空值。

select coalesce(firstname, lastname) as name from users;

或者,您可以使用 case statement :

select case when firstname is not null then firstname else lastname end as name from users;

或者你可以用 if() 功能:

select if(firstname is not null, firstname, lastname) as name from users;

或者你可以用 ifnull() 功能:

select ifnull(firstname, lastname) as name from users;