mysql - 使用 mysql group by 和 where by date 返回计数 0

Question

我想创建一个查询结果数据，如下所示:

但是当我插入 where 子句时，列 name 只是从列 m_ccode 中得出一些值:

问:如果插入 where 子句，如何保留所有 name 列值？

这里是工作 fiddle :

http://sqlfiddle.com/#!9/687776/10

Answer 1

在 on 子句中使用 MONTH(t.date) = '10' AND YEAR(t.date) = '2018' 条件，如下所示

demo

SELECT ccode.name,IFNULL(count(DISTINCT u.username),0) as total_active
,(count(DISTINCT u.username) - count(DISTINCT t.username)) as total_non_active
from m_ccode as ccode
left join m_user as u on u.ccode = ccode.id
left join t_safety_act t on t.username = u.username
and MONTH(t.date) = '10' AND YEAR(t.date) = '2018' group by ccode.id;