sql--查询一天内每小时的数据

一、建一张工具表只有hour一个字段 0-23，或者用mysql自带的mysql.help_topic筛选0-23

二、以0-23的那个为主表左关联，为Null设为0 ifnull(字段,0)

附sql

SELECT
    t.help_topic_id as hour,
    ifNULL(s.number, 0) AS number
FROM
    mysql.help_topic t
LEFT JOIN (
    SELECT
        HOUR (r.capture_time) AS HOUR,
        count(*) AS number
    FROM
        md_capture_record r
    WHERE
        DATE_FORMAT(r.capture_time, '%y-%M-%d') = DATE_FORMAT(NOW(), '%y-%M-%d')
    GROUP BY
        HOUR
) s ON t.help_topic_id = s. HOUR 
 where t.help_topic_id >=0 and t.help_topic_id<24;
ORDER BY hour

 

来源：https://www.cnblogs.com/chaoswu/p/11460231.html