mysql查询，根据时间戳从四个表中排列数据

Question

我试图从四个表中获得有关“类型”的数据。类型可以是注释，封面图片更改，朋友请求接受等，但问题是，我所做的查询不是重复类型的所有和时间戳的所有。我所做的查询是

SELECT c.up_date, c.user_id, c.id, f.id,
       f.up_date, f.friend1, f.friend2, f.status,
       s.postdate, s.status, s.id, s.display_name, s.userid, s.userid1, s.type,
       c.type, f.type
FROM cover_pic c, wp_userstatus s, wp_friends f
WHERE s.userid = f.friend1
AND s.userid = c.user_id
AND f.status =3
AND c.user_id =4
ORDER BY s.postdate
LIMIT 0 , 30

有人能帮我查询时间戳和类型吗？

结果是它给了我

​

​

我想要的

时间戳userid_id id display_name类型 233232323 11顺位者评论 1212121212 1 2顺铂

Answer 1

也许你想要一个连接的union

(select distinct s.postdate as postdate, s.userid, c.id, c.type
 from wp_userstatus s
 join cover_pic c on s.userid = c.user_id)
union
(select distinct s.postdate, s.userid, f.id, f.type
 from wp_userstatus s
 join wp_friends f on s.userid = f.friend1)
order by postdate
limit 30

真的很难分辨。