我正在尝试进行以下查询:
SELECT
DATE_FORMAT( date, '%Y %m' ) AS `Month`,
COUNT( schedule_id ) AS `Shifts`,
COUNT(user_id) AS `Users`
FROM
schedule
GROUP BY
`Month`, `Shifts`
它应该给出一个频率表,说明每月有多少用户工作一定数量的班次(例如,在12月,有10个用户工作20班,12个用户工作15班等)。
但MySQL无法对COUNT()进行分组,因此查询会中断。我怎样才能做到这一点?
答案 0 :(得分:2)
试试这个:
SELECT
`Month`, `Shifts`, COUNT(`User`) `Users`
FROM (
SELECT -- select nr of shifts per user
DATE_FORMAT( date, '%Y %m' ) AS `Month`,
user_id AS `User`,
COUNT( schedule_id ) AS `Shifts`
FROM
schedule
GROUP BY
`Month`, `User`
) s
GROUP BY `Month`, `Shifts`
内部查询返回月份,用户和班次计数。在外部查询中,您可以按班次分组。
答案 1 :(得分:1)
使用子查询获取每个标识符的计数(示例中为列ID),然后将其与原始查询连接
SELECT ... FROM schedule sh JOIN ( SELECT id, COUNT( schedule_id ) AS Shifts FROM schedule ) AS cnt ON cnt.id = sh.id GROUP BY ..., cnt.Shifts
答案 2 :(得分:0)
SELECT
y
, m
, Shifts
, COUNT(*) AS Users
FROM
( SELECT
YEAR(date) AS y
, MONTH(date) AS m
, user_id
, COUNT(*) AS Shifts
FROM
schedule
GROUP BY
YEAR(date), MONTH(date), user_id
) AS grp
GROUP BY
y
, m
, Shifts