mysql - SQL 计算所有行而不是计算单个行

Question

我有一个从数据库请求数据的 SQL 语句。

SELECT `ID`, `To`, `Poster`, `Content`, `Time`, ifnull(`Aura`,0) as `Aura` FROM (
    SELECT * FROM (
        SELECT DISTINCT * FROM messages m
        INNER JOIN
        (
            SELECT Friend2 as Friend FROM friends WHERE Friend1 = '1'
            UNION ALL
            SELECT Friend1 as Friend FROM friends WHERE Friend2 = '1'
        ) friends ON m.Poster = friends.`Friend`
        UNION ALL SELECT DISTINCT *, '1' FROM messages where `Poster`='1'
    ) var
    LEFT JOIN
    (
        select `ID` as `AuraID`, `Status` as `AuraStatus`, count(*) as `Aura`
            from messages_aura
    ) aura ON (var.Poster = aura.AuraID AND var.ID = aura.AuraStatus)
) final

GROUP BY `ID`, `Poster`
ORDER BY `Time` DESC LIMIT 10

这是我的 messages_aura 表格布局。它显示 ID、Status 和 UserID。

这是上述语句的输出。

(上面截图中的ID指的是下面的Poster，上面截图中的Status指的是ID如下)

该语句应为底行指定 Aura 计数 1，为顶行指定 Aura 计数 2。怎么了？

Answer 1

您缺少 GROUP BY，因此它会计算所有内容，而不是按某些列进行分组。

LEFT JOIN
(
    select `ID` as `AuraID`, `Status` as `AuraStatus`, count(*) as `Aura`
    from messages_aura
    GROUP BY AuraID, AuraStatus
) aura ON (var.Poster = aura.AuraID AND var.ID = aura.AuraStatus)