目前,我正在尝试从朋友和/或当前用户所关注的人员中选择帖子列表。但是,当我添加following
表的第二个语句时,我遇到了一个问题。
SELECT * FROM login, threads WHERE login.id=threads.poster_id AND deleted=0 AND login.id
IN ((SELECT CASE WHEN second_id=? THEN first_id ELSE second_id END FROM friends WHERE first_id=? OR second_id=?)
AND (SELECT CASE WHEN follower=? THEN following ELSE follower END FROM following WHERE follower=?))
ORDER BY threads.posted DESC LIMIT 20
只需使用两个明确的IN
条件和两个子查询:
SELECT *
FROM login
INNER JOIN threads
ON login.id = threads.poster_id
WHERE
deleted = 0 AND
(login.id IN (SELECT CASE WHEN second_id=? THEN first_id ELSE second_id END
FROM friends WHERE first_id=? OR second_id=?) AND
login_id IN (SELECT CASE WHEN follower=? THEN following ELSE follower END
FROM following WHERE follower=?))
ORDER BY
threads.posted
DESC LIMIT 20;
这可能会修复语法错误,甚至可以为您提供所期望的输出,但我也觉得我们可以稍微清理一下查询。样本数据将在很长一段时间内实现。