MySQL按小时查询数据，没有的补0

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需求背景

最近的需求，记录一下。一个统计表数据的接口，前端需要返回两个数组，一个是0-23的小时计数，一个是各小时对应的统计数。

思路

  1. 直接使用group by查询要统计的表，当某个小时统计数为0时，会没有该小时分组。思考了一下，需要建立辅助表，只有一列小时，再插入0-23共24个小时
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CREATE TABLE hours_list (
    hour int NOT NULL PRIMARY KEY
)
  1. 先查小时表，再做连接需要查的表，即可将没有统计数的小时填充上0。这里由于需要查多个表中，create_time在每个小时区间内、且SOURCE_ID等于查询条件的统计之和，所以UNION ALL了多张表
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SELECT
    t.HOUR,
    sum(t.HOUR_COUNT) hourCount
FROM
             (SELECT
                 hs. HOUR AS HOUR,
                 COUNT(cs.RECORD_ID) AS HOUR_COUNT
             FROM
                 cbc_hours_list hs
             LEFT JOIN cbc_source_0002 cs ON HOUR (cs.create_time) = hs. HOUR
             AND cs.create_time > #{startTime}
             AND cs.create_time <= #{endTime}
             <#if sourceId?exists && sourceId !=''>
                 AND SOURCE_ID = #{sourceId}
             </#if>
             GROUP BY
                 hs. HOUR
             UNION ALL
             SELECT
                 hs.HOUR AS HOUR,
                 COUNT(cs.RECORD_ID) AS HOUR_COUNT
             FROM
                 cbc_hours_list hs
             LEFT JOIN cbc_source_hs cs ON HOUR (cs.create_time) = hs. HOUR
             AND cs.create_time > #{startTime}
             AND cs.create_time <= #{endTime}
             <#if sourceId?exists && sourceId !=''>
                 AND SOURCE_ID = #{sourceId}
             </#if>
             GROUP BY
                 hs. HOUR
             UNION ALL
             SELECT
                 hs.HOUR AS HOUR,
                 COUNT(cs.RECORD_ID) AS HOUR_COUNT
             FROM
                 cbc_hours_list hs
             LEFT JOIN cbc_source_kfyj cs ON HOUR (cs.create_time) = hs. HOUR
             AND cs.create_time > #{startTime}
             AND cs.create_time <= #{endTime}
             <#if sourceId?exists && sourceId !=''>
                 AND SOURCE_ID = #{sourceId}
             </#if>
             GROUP BY
                 hs. HOUR
             UNION ALL
             SELECT
                 hs.HOUR AS HOUR,
                 COUNT(cs.RECORD_ID) AS HOUR_COUNT
             FROM
                 cbc_hours_list hs
             LEFT JOIN cbc_source_his_0002 cs ON HOUR (cs.create_time) = hs. HOUR
             AND cs.create_time > #{startTime}
             AND cs.create_time <= #{endTime}
             <#if sourceId?exists && sourceId !=''>
                 AND SOURCE_ID = #{sourceId}
             </#if>
             GROUP BY
                 hs. HOUR
             UNION ALL
             SELECT
                 hs.HOUR AS HOUR,
                 COUNT(cs.RECORD_ID) AS HOUR_COUNT
             FROM
                 cbc_hours_list hs
             LEFT JOIN cbc_source_his_hs cs ON HOUR (cs.create_time) = hs. HOUR
             AND cs.create_time > #{startTime}
             AND cs.create_time <= #{endTime}
             <#if sourceId?exists && sourceId !=''>
                 AND SOURCE_ID = #{sourceId}
             </#if>
             GROUP BY
                 hs. HOUR
             UNION ALL
             SELECT
                 hs.HOUR AS HOUR,
                 COUNT(cs.RECORD_ID) AS HOUR_COUNT
             FROM
                 cbc_hours_list hs
             LEFT JOIN cbc_source_his_kfyj cs ON HOUR (cs.create_time) = hs. HOUR
             AND cs.create_time > #{startTime}
             AND cs.create_time <= #{endTime}
             <#if sourceId?exists && sourceId !=''>
                 AND SOURCE_ID = #{sourceId}
             </#if>
             GROUP BY
                 hs. HOUR) t
         GROUP BY
             t.hour

效果

统计数为0的小时也可以查出来了。

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