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这篇文章首要介绍了MySQL按小时查询数据,工信部网站备案没有的补0,本文通过实例代码给我们介绍的十分详细，对我们的学习或作业具有必定的参阅学习价值，需求的朋友可以参阅下

需求布景

一个计算接口，前端需求返回两个数组，一个是0-23的小时计数，一个是各小时对应的计算数。

思路 直接运用group by查询要计算的表，当某个小时计算数为0时，会没有该小时分组。思考了一下，需求树立辅助表，只要一列小时，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，再做连接需求查的表，即可将没有计算数的小时填充上0。这里由于需求查多个表中，create_time在每个小时区间内、且SOURCE_ID等于查询条件的计算之和，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}

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}

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}

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}

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}

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}

GROUP BY
hs. HOUR) t
GROUP BY
t.hour

作用

计算数为0的小时也可以查出来了。

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