Question

我想根据表格中的条件订购Postgres查询

    id   sensor_id            alarmTime            clearedTime
415068        3734  2016-04-20 12:25:32    2016-04-27 21:05:44  
415070        3734  2016-04-21 12:25:32                   null
415071        3734  2016-03-22 12:25:32    2016-04-29 21:15:44          
415072        3734  2016-04-23 12:25:32                   null          
415073        3734  2016-04-20 12:25:32    2016-04-22 22:05:45          
415074        3734  2016-02-26 12:25:32    2016-04-27 23:15:24

从上面的表格中，我想首先按空值排序，然后按报警时间排序，其余行仅按清除时间排序。得到这样的东西

    id   sensor_id            alarmTime            clearedTime
415070        3734  2016-04-21 12:25:32                   null
415072        3734  2016-04-23 12:25:32                   null  
415068        3734  2016-04-20 12:25:32    2016-04-27 21:05:44  
415073        3734  2016-04-20 12:25:32    2016-04-22 22:05:45          
415071        3734  2016-03-22 12:25:32    2016-04-29 21:15:44          
415074        3734  2016-02-26 12:25:32    2016-04-27 23:15:24

我尝试过这样的事情

select * from table
ORDER BY
case alarm.clearedTime is NOT NULL
when TRUE THEN alarmTime
else clearedTime
end  DESC NULLS FIRST;

Answer 1

尝试

ORDER BY COALESCE(clearedTime, alarmTime)

或类似的东西。

ORDER BY CASE 
             WHEN clearedTime IS NULL THEN NULL
                                      ELSE 1 
         END NULLS FIRST,
         alarm.alarmTime DESC,
         alarm.clearedTime DESC -- optional to solve tie between 415068 and 415073

Answer 2

这个怎么样？

order by alarm.clearedTime nulls first, alarm.alarmTime

Postgres按条件排序多列

2 个答案: