mysql 按月统计但是有几个月没有数据，需要变成0

创建现在倒过去的12个月的视图

CREATE VIEW `past_12_month_view` AS
SELECT DATE_FORMAT(CURDATE(), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 1 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 2 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 3 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 4 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 5 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 6 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 7 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 8 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 9 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 10 MONTH), '%Y-%m') AS `month`
UNION SELECT DATE_FORMAT((CURDATE() - INTERVAL 11 MONTH), '%Y-%m') AS `month`

写出自己的sql

SELECT DATE_FORMAT(create_date,'%Y-%m') as paTime,COUNT(a.create_date) as xunNum from patrol_record a GROUP BY paTime /*日常巡查*/

 

左链接

select t.month as paTime,
ifNull(b.xunNum,0) as xunNum from past_12_month_view t LEFT JOIN
(SELECT DATE_FORMAT(create_date,'%Y-%m') as paTime,COUNT(a.create_date) as xunNum from patrol_record a GROUP BY patime) b
on b.paTime=t.month /*日常巡查*/