单个查询中的多个 select 语句

Question

目前，我正在尝试 select 当前用户关注的朋友 and/or 的帖子列表。但是，当我在 following table.

的第二个语句中添加时，我运行遇到了问题

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

Answer 1

只需对两个子查询使用两个显式 IN 条件：

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，甚至会为您提供您期望的输出，但我也觉得我们可能能够进一步清理查询。样本数据将大大有助于实现这一目标。

单个查询中的多个 select 语句

Multiple in select statements in single query

mysql

adodb