mysql 根据当前日期，查询24个小时每小时的数量，为null填充0

1、时间字段是datetime类型

2、需要用到中间表，表结构和数据链接下载

链接：https://pan.baidu.com/s/1tAFU4nm1p4CkSneXwceA_A 
提取码：b3xi

3、sql

select
    CREATEDATE as YYmmdd,
    CONCAT(CREATEDATE,‘ ‘,d.i) YYmmddHH,
    d.i as HH,
    case when zscum is null then 0 else zscum end as zscum
from
    (
    select
    DATE_FORMAT(CREATEDATE,‘%Y-%m-%d‘) as CREATEDATE,
    SUM(CASE WHEN e.status = ‘1‘ THEN 1 ELSE 0 END ) AS zscum,
    HOUR ( CREATEDATE ) as hour
    from event_base_info e
    -- 自己的条件
    where e.status=‘1‘ and  e.STATE not in(‘3702820001‘)
    -- 时间
    and DATE_FORMAT( CREATEDATE, ‘%Y-%m-%d‘ ) like ‘2019-06-04%‘
    GROUP BY HOUR ( CREATEDATE )
    ) o
    -- 中间表
    RIGHT JOIN ( select i from num where i between ‘0‘ and ‘24‘ ) d on o.hour = d.i
GROUP BY d.i

5、效果 （HH是小时，用了中间表）

如有疏漏，请指正！谢谢

原文地址：https://www.cnblogs.com/w-yu-chen/p/10976792.html