MySQL按小时查询数据,没有的补0

一个统计接口，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 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

CREATE TABLE hours_list (
 hour int NOT NULL PRIMARY KEY
)

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

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

统计数为0的小时也可以查出来了。