php - 每个月的Mysql计数

Question

我有一个 mysql 表，如下所示:

id      level      time
1         1     2014-02-19 04:33:04
2         1     2014-03-19 04:33:04
3         1     2014-03-20 04:33:04
4         2     2014-03-21 04:53:04
5         1     2014-07-19 04:33:04
6         2     2014-07-19 04:33:04
7         1     2014-07-19 04:33:04
8         1     2014-08-19 04:33:04

我想像这样获得第 1 级的结果:

level1count    year    month
  0            2014      1
  1            2014      2
  2            2014      3
  0            2014      4
  0            2014      5
  0            2014      6
  2            2014      7
  1            2014      8
  0            2014      9
  0            2014      10
  0            2014      11
  0            2014      12

我试过这个查询，但没有给出每个月的结果

SELECT YEAR(time) AS year, MONTH(time) AS month, COUNT(DISTINCT id) AS count FROM users where level = '1' GROUP BY year, month

Answer 1

您正在寻找的是让所有月份的结果在数据库中存在或不存在，对于结果集，您需要像 union 一样在查询中拥有所有月份，然后使用基于年份和月份的条件与您的表联接

select coalesce(sum(`level` = 1),0) level1count
 coalesce(sum(`level` = 2),0) level2count ,y,m
from
(select 1 as m,2014 as y
union
.
.
.
union
select 12 as m ,2014 as y
) months
left join t on(months.m = month(t.time) and months.y = year(t.time))
group by months.m, year(t.time)

Demo

比 union 更好的方法是有一个包含所有月份和年份行的表，然后将它与你的表连接