mysql - 从事件中选择不同的值

Question

我有下面这 3 个表格，我想列出所有赢得金牌的运动员

Athletes
    +------------+-----------------+
    | athletesID | athletesName    |
    +------------+-----------------+
    | jg         | justin gatlin   |
    | ms         | maria sharapova |
    | ub         | usain bolt      |
    | vw         | venus williams  |
    +------------+-----------------+

events
    +---------+-----------+---------------------+
    | eventID | eventName | athletes_athletesID |
    +---------+-----------+---------------------+
    | ev1     | tennis    | ms                  |
    | ev1     | tennis    | vw                  |
    | ev2     | mens 100m | jg                  |
    | ev2     | mens 100m | ub                  |
    +---------+-----------+---------------------+
results

    +-----------+--------+----------------+----------------------------+
    | resultsID | Medal  | events_eventID | events_athletes_athletesID |
    +-----------+--------+----------------+----------------------------+
    | results1  | silver | ev1            | ms                         |
    | results1  | Gold   | ev1            | vw                         |
    | results2  | silver | ev2            | jg                         |
    | results2  | Gold   | ev2            | ub                         |
    +-----------+--------+----------------+----------------------------+

到目前为止，我已经使用了下面的代码，但这列出了所有银牌获得者都赢得了金牌

SELECT 
    athletesID, athletesName, medal
FROM
    myoly.athletes
        JOIN
    myoly.events ON athletes.athletesID = events.athletes_athletesID
        JOIN
    myoly.results ON myoly.events.eventID = myoly.results.events_eventID
WHERE
    medal = 'gold';

如何列出所有仅赢得金牌的运动员？

Answer 1

SELECT 
    a.athletesID, 
    a.athletesName, 
    r.medal
FROM results r
LEFT JOIN athletes a
ON a.athletesID  = r.events_athletes_athletesID 
WHERE r.medal = 'Gold';