SQL - 两个日期之间的条件

Question

我有一个包含 3 列的表：user_id、start_date、cancellation_date

我想获得 4 列： Date、Number of Active Users、Number of Users Who Canceled、Cancellation Rate

关于如何编写查询的任何想法？

提前致谢！

Answer 1

这是衡量新用户、取消用户、活跃用户的一种方法：

SELECT  calendar_date,
        (SELECT COUNT(*) FROM users AS usr WHERE cal.calendar_date BETWEEN usr.start_date AND IFNULL(usr.cancellation_date, '3000-01-01')) AS active_users,
        (SELECT COUNT(*) FROM users AS usr WHERE usr.start_date = cal.calendar_date) AS new_users,
        (SELECT COUNT(*) FROM users AS usr WHERE usr.cancellation_date = cal.calendar_date) AS users_cancelled
FROM    my_calendar AS  cal

（假设您有包含所有日期的表“my_calendar”）

Answer 2

如果我们定义活跃用户为cancellation_date为null，查询会是这样的；

SELECT 
( SELECT CURDATE() ) AS `DATE`,
( SELECT COUNT(*) FROM users WHERE cancellation_date IS NULL) AS `Number of active users`,
( SELECT COUNT(*) FROM users WHERE cancellation_date IS NOT NULL) AS `number of users who cancelled`,
( SELECT `number of users who cancelled` / (`Number of active users` + `number of users who cancelled`)) AS `cancellation rate`

在 MySQL 8 上测试，https://www.db-fiddle.com/f/6QPLn2C79rnzrfN71i1GMV/0