我有一张桌子,床身ID有多个不同的状态,就像这样.
PID | term_id | student_id | bed_id | status | Comment
--------+------------+---------------+-----------+-----------+----------------
1 | 29 | 1234 | 751 | Canceled | Not this one
2 | 29 | 1234 | 751 | Active | This one
3 | 29 | 531 | 752 | Active | This one too
4 | 29 | 823 | 752 | Canceled | Not this one either
5 | 29 | 525 | 753 | Canceled | But this one too
我想要一个查询,根据状态值为每个bed_id获取一行.
我试过了：
SELECT *,MIN(CASE sample.status
WHEN 'Arrived' THEN 1
WHEN 'Active' THEN 2
WHEN 'Pending Approval' THEN 3
WHEN 'Pending Confirmation' THEN 4
WHEN 'Pending Manual' THEN 5
WHEN 'Denied' THEN 6
WHEN 'Canceled' THEN 7
END) AS StatusOrder
FROM sample
WHERE (sample.term_id = 29)
GROUP BY bed_id
但它给了我：
PID | term_id | student_id | bed_id | status | Comment | StatusOrder
------------------------------------------------------------------------------------
1 | 29 | 1234 | 751 | Canceled | Not this one | 2
3 | 29 | 531 | 752 | Active | This one too | 2
5 | 29 | 525 | 753 | Canceled | But this one too | 7
(StatusOrder值是正确的,但行的其余部分与具有最小StatusOrder值的行不对应)
我想要的是：
PID | term_id | student_id | bed_id | status | Comment | StatusOrder
------------------------------------------------------------------------------------
2 | 29 | 1234 | 751 | Active | This one | 2
3 | 29 | 531 | 752 | Active | This one too | 2
5 | 29 | 525 | 753 | Canceled | But this one too | 7
我读过MySQL MIN/MAX all row
并试过这个：
SELECT *,MIN(CASE sample.status
WHEN 'Arrived' THEN 1
WHEN 'Active' THEN 2
WHEN 'Pending Approval' THEN 3
WHEN 'Pending Confirmation' THEN 4
WHEN 'Pending Manual' THEN 5
WHEN 'Denied' THEN 6
WHEN 'Canceled' THEN 7
END) AS StatusOrder
FROM sample
WHERE (
(sample.term_id = 29) AND (
StatusOrder = CASE sample.status
WHEN 'Arrived' THEN 1
WHEN 'Active' THEN 2
WHEN 'Pending Approval' THEN 3
WHEN 'Pending Confirmation' THEN 4
WHEN 'Pending Manual' THEN 5
WHEN 'Denied' THEN 6
WHEN 'Canceled' THEN 7
END)
)
GROUP BY bed_id
但这会产生错误. (还尝试用完整的CASE语句替换StatusOrder)
注意：我已经简化了具有更多列的实际表.但基本上我需要访问每个bed_id对应于具有最低StatusOrder(由我的case语句确定)的行的整行.
使用MysqL 5.5
最佳答案
下面的查询工作正常,但最好考虑用status_code替换列状态和代码,并具有单独的表状态(status_code,description){denormalise}
原文链接：https://www.f2er.com/mysql/434265.html和索引(term_id,statUs_code).
通过这个,我们可以自己加入.而是创建这样的视图.
SELECT * FROM
(SELECT *,(CASE sample.status
WHEN 'Arrived' THEN 1
WHEN 'Active' THEN 2
WHEN 'Pending Approval' THEN 3
WHEN 'Pending Confirmation' THEN 4
WHEN 'Pending Manual' THEN 5
WHEN 'Denied' THEN 6
WHEN 'Canceled' THEN 7
END) AS status_code FROM SAMPLE
WHERE sample.term_id = 29
) my_view1,(SELECT BED_ID,MIN(CASE sample.status
WHEN 'Arrived' THEN 1
WHEN 'Active' THEN 2
WHEN 'Pending Approval' THEN 3
WHEN 'Pending Confirmation' THEN 4
WHEN 'Pending Manual' THEN 5
WHEN 'Denied' THEN 6
WHEN 'Canceled' THEN 7
END) AS status_code FROM SAMPLE
WHERE sample.term_id = 29
GROUP BY BED_ID
) my_view2
WHERE my_view1.bed_id = my_view2.bed_id
AND my_view1.status_code = my_view2.status_code