mysql 连接查询总和返回 null

Question

如果 makale_ payments 表为 null，则查询返回 null。如果 SUM( payment_total ) 中不存在像 0.00 这样的值，我应该如何设置查询来获取记录？

SELECT article_name,user_real_name,user_name,SUM(`article_payment`) as holding,paid
FROM makale_articles AS t1
JOIN makale_users ON (t1.article_name=makale_users.user_id) 
JOIN (SELECT user_id,SUM(`payment_total`) as paid FROM makale_payments GROUP BY user_id) AS t2 ON (t1.article_name=t2.user_id)
GROUP BY t2.user_id

Answer 1

这就是 IFNULL 的用途:

IFNULL(SUM(...), 0.0)