MySQL按小时查询数据,没有的补0

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

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

效果

统计数为0的小时也可以查出来了。

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