我正在使用 MySQL。
我有一个表 service_status
:
id | service_id | service_status
----------------------------------------------------------------------
0 | 1001 | download_started
1 | 1001 | download_started
2 | 1002 | download_started
3 | 1002 | download_started
4 | 1002 | download_failed
5 | 1003 | download_started
6 | 1003 | download_failed
7 | 1003 | something_else
8 | 1003 | another_thing
我要查询所有service_id
s,以及两个附加列,用于计算 download_started
的数量和数量download_failed
:
id | service id | download_started | download_failed
----------------------------------------------------------------------
0 | 1001 | 2 | 0
1 | 1002 | 2 | 1
2 | 1003 | 1 | 1
我只关心 download_started
的状态或download_failed
.
非常感谢。
最佳答案
你可以使用这个:
SELECT
service_id,
SUM(CASE WHEN service_status = 'download_started' THEN 1 ELSE 0 END) download_started,
SUM(CASE WHEN service_status = 'download_failed' THEN 1 ELSE 0 END) download_failed
FROM
table_name
GROUP BY
service_id
ORDER BY
service_id;
关于mysql - 如何在SQL中有效地统计某些列值的出现次数?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/42239603/