mysql - SQL 查询未按预期工作 |重复和错误的结果

Question

嘿伙计们。

好吧，所以我正在这里处理这个小代码片段

        SELECT 
                current.name, 
                current.status, 
                current.votes,
                current.info, 
                current.votes_required, 
                current.sid as sid,
                current.previous_required,
                previous.sid as psid,
                previous.status as status
            FROM
                systems as current
            INNER JOIN
                systems as previous
            WHERE
                (previous.status = 1 and current.previous_required = previous.status)
                OR
                (current.previous_required = 0)
            '

理想情况下，我希望显示 previous_required == 0 或 previous_required 的状态 == 1 的结果。但是，由于某种原因，我要么从搜索中获得三倍的结果(EG 重复项)，要么只获得一个第一个结果为单个结果。

我非常确定我知道我哪里搞砸了(要么是内连接，要么是 OR 语句)。但我似乎无法确定并解决问题。任何意见将不胜感激。

Answer 1

您需要将条件从加入位置移动

    SELECT 
            current.name, 
            current.status, 
            current.votes,
            current.info, 
            current.votes_required, 
            current.sid as sid,
            current.previous_required,
            previous.sid as psid,
            previous.status as status
        FROM
            systems as current
        INNER JOIN
            systems as previous
          ON
            (previous.status = 1 and current.previous_required = previous.status)
            OR
            (current.previous_required = 0)