如何在Oracle中按日期分组和排序？

Question

I run this SQL request:

SELECT Max(scaleA.val) AS scaleA_val,
       Max(scaleB.val) AS scaleB_val,
       To_char(From_dt1970(scaleA.time1970), 'DD') AS day
  FROM rsdu2elarh.el008_6305119 scaleA
  FULL OUTER JOIN rsdu2elarh.el008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > To_dt1970(To_date('2019/11/01', 'yyyy/mm/dd'))
   AND scaleA.time1970 < To_dt1970(To_date('2019/12/01', 'yyyy/mm/dd'))
 GROUP BY 'day'
 ORDER BY 'day'

and return it:

But it is not sorted by date. How to make the request display data sorted by date? All my attempts result in "not a group by expression" or many repeated fields :(

Answer 1

If you use GROUP BY clause, any expression in SELECT or ORDER BY, which is not group function (or aggregate function or aggregated column) such as COUNT, AVG, MIN, MAX, SUM and so on (List of Aggregate functions) should be present in GROUP BY clause.

Example 1: (here employee_id is not group function , so it must appear in GROUP BY. By contrast, sum(salary) is a group function (aggregated column), so it is not required to appear in the GROUP BYclause.

SELECT employee_id, sum(salary) 
FROM employees
GROUP BY employee_id
ORDER BY employee_id; 

Example 2: This will lead to the "not a group by expression" error .

SELECT employee_id, sum(salary) 
FROM employees;  

To correct you need to do one of the following :

Include all non-aggregated expressions listed in SELECT and ORDER BY clause in the GROUP BY clause.

Answer 2

You can not order by with the column which is not groupped because same date may appear in more than one group so if you want order by DD then you can use it in order by clause as following:

SELECT  MAX(scaleA.VAL) AS scaleA_val, MAX(scaleB.VAL) AS scaleB_val FROM RSDU2ELARH.EL008_6305119 scaleA 
FULL OUTER JOIN RSDU2ELARH.EL008_6305126 scaleB ON scaleA.time1970 = scaleB.time1970 
WHERE scaleA.time1970 > TO_DT1970(TO_DATE ('2019/11/01', 'yyyy/mm/dd')) AND scaleA.time1970 < TO_DT1970(TO_DATE ('2019/12/01', 'yyyy/mm/dd')) 
GROUP BY TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')
-- use this order by clause
Order by TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')

Cheers!!

Answer 3

You can try to add TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD') also into the SELECT list, alias it and use within ORDER BY Clause :

SELECT TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD') AS myDay,
       MAX(scaleA.VAL) AS scaleA_val, 
       MAX(scaleB.VAL) AS scaleB_val
  FROM RSDU2ELARH.EL008_6305119 scaleA
  FULL OUTER JOIN RSDU2ELARH.EL008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > TO_DT1970(DATE'2019-11-01')
   AND scaleA.time1970 < TO_DT1970(DATE'2019-12-01')
 GROUP BY TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')
 ORDER BY myDay

while column alias cannot be used for GROUP BY Clause.

Answer 4

The only missing thing in your query is that we cannot use an alias in the group by clause, but alias can be used in order by clause so below query will work.

SELECT Max(scaleA.val) AS scaleA_val,
       Max(scaleB.val) AS scaleB_val,
       To_char(From_dt1970(scaleA.time1970), 'DD') AS day
  FROM rsdu2elarh.el008_6305119 scaleA
  FULL OUTER JOIN rsdu2elarh.el008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > To_dt1970(To_date('2019/11/01', 'yyyy/mm/dd'))
   AND scaleA.time1970 < To_dt1970(To_date('2019/12/01', 'yyyy/mm/dd'))
 GROUP BY To_char(From_dt1970(scaleA.time1970), 'DD')
 ORDER BY day;

If You want to use an alias then you need to use a subquery

SELECT Max(scaleA_val)  AS scaleA_val,
       Max(scaleB_val) AS scaleB_val,
       day from
       (select scaleA.val  scaleA_val,
        scaleB.val AS scaleB_val,
        To_char(From_dt1970(scaleA.time1970), 'DD') AS day
  FROM rsdu2elarh.el008_6305119 scaleA
  FULL OUTER JOIN rsdu2elarh.el008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > To_dt1970(To_date('2019/11/01', 'yyyy/mm/dd'))
   AND scaleA.time1970 < To_dt1970(To_date('2019/12/01', 'yyyy/mm/dd'))
   )
 GROUP BY day
 ORDER BY day;