我有 3 张 table :
成员(网卡,名称)
奖项(nic,aw_name)
冠军(nic,ch_name)
一个人可以拥有多个奖项或冠军。例如理查德有2个奖项和3个冠军,而史蒂夫没有任何奖项或冠军。
现在我想列出获得奖项和冠军的人员名单。例如:
| nic | name | aw_name | ch_name |
|----------|------------|-------------|-------------------|
| 1 | Richard | award 1 | championship 1 |
| 1 | Richard | award 2 | championship 2 |
| 1 | Richard | | championship 3 |
| 2 | Steve | | |
谁能帮帮我吗?谢谢!
最佳答案
试试这个:
SELECT
members.nic,
members.name,
awards.aw_name,
championships.ch_name
FROM
(
SELECT
CASE WHEN @curNic = members.nic THEN @curRow := @curRow + 1 ELSE @curRow := 1 END num,
@curNic := members.nic nic,
name
FROM
members LEFT JOIN
(
SELECT nic FROM awards UNION ALL
SELECT nic FROM championships
) tmp ON tmp.nic = members.nic JOIN
(SELECT @curNic := null, @curRow := 0) r
) members LEFT JOIN
(
SELECT
CASE WHEN @curNic1 = nic THEN @curRow1 := @curRow1 + 1 ELSE @curRow1 := 1 END num,
@curNic1 := nic nic,
aw_name
FROM
awards JOIN
(SELECT @curNic1 := null, @curRow1 := 0) r
) awards ON awards.nic = members.nic AND awards.num = members.num LEFT JOIN
(
SELECT
CASE WHEN @curNic2 = nic THEN @curRow2 := @curRow2 + 1 ELSE @curRow2 := 1 END num,
@curNic2 := nic nic,
ch_name
FROM
championships JOIN
(SELECT @curNic2 := null, @curRow2 := 0) r
) championships ON championships.nic = members.nic AND championships.num = members.num
WHERE
awards.nic IS NOT NULL OR championships.nic IS NOT NULL OR members.num = 1
如果mysql中有FULL OUTER JOIN会更容易,但是没有。
关于mysql - 如何在mysql中左连接3个表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20043720/