sql查询每个季度的数据并自动补零

对表中每个季度的数据进行统计并实现自动补零，首先先查询出表中每个季度的数据

SELECT QUARTER(applicationdate) as mon, COUNT(*) as con FROM qm_technical_zero GROUP BY QUARTER(applicationdate)

从表qm_technical_zero中按季度查询日期applicationdate的数据，但是只能出现前三季度的数据，第四季度为零所以不显示。

结果如下所示

然后在建立一个表

SELECT  1 as click_date UNION ALL
SELECT  2 as click_date UNION ALL
SELECT  3 as click_date UNION ALL
SELECT  4 as click_date

结果如下图所示

然后对两个表进行联合查询就可以实现补零操作。
 

SELECT click_date as q,IFNULL(b.con,0) as c FROM(SELECT  1 as click_date UNION ALL
SELECT  2 as click_date UNION ALL
SELECT  3 as click_date UNION ALL
SELECT  4 as click_date) a LEFT JOIN(
SELECT QUARTER(applicationdate) as mon, COUNT(*) as con FROM qm_technical_zero GROUP BY QUARTER(applicationdate))
b ON click_date=b.mon

进行联合查询后结果如下所示：