需求背景
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
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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
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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) tGROUP BY t.hour |
效果
统计数为0的小时也可以查出来了。
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原文链接：https://blog.csdn.net/Princar/article/details/111302667
