Question

我有两个MySQL表赞助和事件。我想显示一个赞助商列表，按照他们赞助的活动类别排序，但只在每个活动下展示一次赞助。样本连接表：

SPONSORSHIPS
sponsorhipid | sponsorid | eventid | date       | 
-------------|-----------|---------|------------|
1            | 3         |  20     | 06/01/2013 |
2            | 2         |  20     | 06/02/2013 |
3            | 3         |  20     | 06/03/2013 |
4            | 2         |  21     | 06/04/2013 |

EVENTS
eventid | name      | premium    | 
--------|-----------|------------|
20      | Lunch     | 0          | 
21      | Dinner    | 1          |

JOIN的结果是：

sponsorhipid | sponsorid | eventid | date       | name    | premium  | 
-------------|-----------|---------|------------|---------| ---------|
1            | 3         |  20     | 06/01/2013 | Lunch   | 0        |
2            | 2         |  20     | 06/02/2013 | Lunch   | 0        |
4            | 2         |  21     | 06/04/2013 | Dinner  | 1        |

我尝试了DISTINCT和GROUP BY但是这些事件已经崩溃了，所以如果赞助商＃2赞助两个不同的活动，他们仍然只会展示一次。我怎样才能做到这一点？这是我最后一次SQL查询：

SELECT DISTINCT (sponsorships.sponsorshipid), sponsorships.*, events.*
            FROM events 
            INNER JOIN sponsorships
            ON events.eventid = sponsorships.eventid

非常感谢任何指针！

Answer 1

您需要使用这样的嵌套子查询：

SELECT s.sponsorhipid, s.sponsorid, s.eventid, s.date
       ,e.name, e.premium
FROM EVENTS e 
JOIN
(
    SELECT s1.* FROM SPONSORSHIPS s1
    JOIN
    (
      SELECT sponsorid, MIN(Date) As minDate
      FROM SPONSORSHIPS
      GROUP BY eventid,sponsorid
    ) s2
    ON s1.sponsorid = s2.sponsorid
    AND s1.date = s2.minDate
) s
ON e.eventid = s.eventid;

输出：

| SPONSORHIPID | SPONSORID | EVENTID |       DATE |   NAME | PREMIUM |
|--------------|-----------|---------|------------|--------|---------|
|            1 |         3 |      20 | 06/01/2013 |  Lunch |       0 |
|            2 |         2 |      20 | 06/02/2013 |  Lunch |       0 |
|            4 |         2 |      21 | 06/04/2013 | Dinner |       1 |

在具有6列的连接中获取两列的不同记录

1 个答案:

请参阅this SQLFiddle