如图:上面实现的是从表oilwell_backpressure 中查询字段oilwell_name="王新66侧",在字段oilwell_date="2013-07-30" 10:00到11:00间,字段backpressure,值最大对应的那行记录。如果我要实现从0:00到24:00每间隔一小时取一个这样的最大值,对应的那行的记录,这个语句该怎么写啊sql多行子查询
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select max(backpressure) val,substring(oilwell_time, 1,2) hou, oilwell_date from oilwell_backpressure where oilwell_name ='王新66侧' and oilwell_date ='2013-08-09' group by substring(oilwell_time, 1,2), oilwell_date order by oilwell_date, hou