sql - 如何为另一个表中的所有组重复表中的所有行？

Question

如何为另一个表中的所有组重复表中的所有行？

Answer 1

从指定日期执行简单的 SELECT COUNT？

SELECT month_start, next_month_start, sum(cnt) as users, dept FROM
(SELECT CASE WHEN created_at<=next_month_start AND created_at>=month_start THEN 1 ELSE 0 END as cnt,
users.*, month_start, next_month_start FROM users
CROSS JOIN dates) as S1
GROUP BY dept, month_start, next_month_start ORDER BY dept DESC