mysql每隔45分钟分组查找时间段内最大与最小数据的差值

mysql每隔45分钟分组查找时间段内最大与最小数据的差值

关键点在于case 先让 子查询 在确定时间后执行不然必失败为null,

子查询的优先度为第二,第一是from后的基表,然后是子查询然后是字段

要子查询在字段后执行使用case延后子查询的优先度

       set @dates := DATE_sub(date_format('2021-12-01 17:15:00', '%Y-%m-%d 00:00'), interval 45 minute);
        set @dates1:= date_format('2021-12-01 17:15:00', '%Y-%m-%d 00:00');
       select allop.time,allop.nums  from(
        select tc22.tc1 as time,tc22.tc2,(case when
                                 tc1!=tc2
                                 then
                                (select uio from
                                (select ifnull(max(code_05),0)-if((min(code_05)is null) or min(code_05)=0,ifnull(max(code_05),0),min(code_05)) as uio
                                from zkyq_efe.ele_enterprise_data where enterprise_id = '302373134751760384'
                                and data_time>=
                                tc1
                                 and data_time <=
                                tc2
                                order by code_05 desc
                                limit 1
                                 ) as tccc) else tc1 end)as nums
        from    (select (@dates := DATE_ADD(@dates, interval 45 minute)) as tc1,
                    (@dates1:= DATE_ADD(@dates1, interval 45 minute)) as tc2
                from zkyq_efe.ele_enterprise_data
                 limit 32) as tc22 )as allop