MySQL INNER JOIN 别名

Posted 2023-02-24

【中文标题】MySQL INNER JOIN 别名

【英文标题】：MySQL INNER JOIN Alias

【发布时间】：2012-05-30 06:14:20

【问题描述】：

有谁知道我如何在其中进行内部连接和别名值，这样它们就不会相互覆盖？如果您看到我的代码，它可能看起来更清楚：

    SELECT  home, away, g.network, g.date_start 
    FROM    game g
    INNER JOIN team t ON (
        (t.importid = g.home) as home
        OR
        (t.importid = g.away) as away
    )
    ORDER BY date_start DESC 
    LIMIT 7

已解决（下面的帮助是我的最终查询）

    SELECT 
        home.market AS home_market, 
        away.market AS away_market, 
        g.network, 
        g.date_start

    FROM game AS g
    INNER JOIN team AS home ON (
        home.importid = g.home
    )
    INNER JOIN team AS away ON (
        away.importid = g.away
    )

    ORDER BY g.date_start DESC 
    LIMIT 7

【参考方案1】：

您需要参加两次：

SELECT home.*, away.*, g.network, g.date_start 
FROM game AS g
INNER JOIN team AS home
  ON home.importid = g.home
INNER JOIN team AS away
  ON away.importid = g.away
ORDER BY g.date_start DESC 
LIMIT 7

【参考方案2】：

使用单独的列来表示连接条件

SELECT  t.importid, 
        case 
            when t.importid = g.home 
            then 'home' 
            else 'away' 
        end as join_condition, 
        g.network, 
        g.date_start 
FROM    game g
INNER JOIN team t ON (t.importid = g.home OR t.importid = g.away)
ORDER BY date_start DESC 
LIMIT 7

【讨论】：

嘿，这很酷——但我试图将“家”和“离开”放在同一行。我知道我的问题没有太大意义。 :) 如果我想要单独的主/行记录，这确实有效。