我有一个表，其中床ID的多个值具有不同的状态，类似这样。
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
我希望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
但这给了我:
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值正确，但其余行与StatusOrder值最小的行不对应)
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
并尝试了这个:
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。 (也尝试用完整的CASE语句替换StatusOrder)
注意:我已经简化了具有更多列的实际表。但是基本上，我需要访问与每个bed_id具有最低StatusOrder(由我的case语句确定)的行相对应的整行。
使用MySQL 5.5
最佳答案
以下查询有效，但最好考虑将status_code的列状态替换为代码，并使用单独的表status(status_code,description) {denormalise}
并建立索引(term_id,statUs_code)。
这样，我们就可以自我加入。而是创建一个这样的 View 。
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
关于mysql - SQL根据计算列的最小值获取整个行，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/20822574/