mysql 在同一个表上组合不同的 count()

Question

我的数据库包含一个“lastOnline”时间戳变量，它在用户登录时获取更新。我想用它来检索 3 个值

[The total amount of users][users online today][users online in the last hour].

我可以单独做每个语句

SELECT count(u.id) AS usersTotal FROM user u

SELECT count(u.id) AS usersDay FROM user u
WHERE u.lastOnline >= now() - INTERVAL 1 DAY

SELECT count(u.id) AS usersHour FROM user u
WHERE u.lastOnline >= now() - INTERVAL 1 HOUR

但我无法将其中 3 个加入/联合到一个查询中

谢谢

Answer 1

你可以使用:

SELECT count(u.id) AS usersTotal 
      ,SUM(u.lastOnline >= now() - INTERVAL 1 DAY)  AS usersDay
      ,SUM(u.lastOnline >= now() - INTERVAL 1 HOUR) AS usersHour
FROM user u;

工作原理:

u.lastOnline >= now() - INTERVAL 1 DAY 返回 true(1) 或 false(0)。