如果條件裏面MySQL查詢

Question

我需要給條件MySQL查詢裏面，

select IF(r.name=NULL,'customer',r.name) as previlage 
from users u LEFT JOIN role r on r.rid = u.uid ORDER BY u.created DESC\G 

我需要檢查if the r.name field is null then it should be displayed as customer，但現在if r.name is NULL then its displayed as null itself。我怎樣才能做到這一點，謝謝。

Answer 1

你不能=比較NULL，你需要使用is null

r.name is null 

，而不是

r.name=NULL 

https://dev.mysql.com/doc/refman/5.0/en/working-with-null.html