Oracle sql 先排序较大的日期，基于2个日期列

Question

I have table which contains 2 columns CREATION_DATE AND CHANGE_DATE. I am looking for a way to sort data based on date which is greater.

May be like:

select * from table order by compare(CREATION_DATE ,CHANGE_DATE) desc;

the compare(CREATION_DATE,CHANGE_DATE) function suppose to return greater date between both columns.

I have search a lot and tried various combination with date function and NULLS FIST, LAST but not use.

any help is greatly appreciated.

Answer 1

If neither date is NULL , then you can use:

order by greatest(creation_date, change_date) desc

Unfortunately, greatest() returns NULL if any value is NULL .

If change_date is either NULL or bigger than creation_date , then you can use coalesce() :

order by coalesce(change_date, creation_date)

This situation makes sense to me -- changing something before it is created is unusual.

If change_date can be NULL and can also be less than creation_date , then you need to be more careful. You need to replace by a value. Presumably, creation_date would not be NULL and you can use coalesce() :

order by greatest(creation_date, coalesce(change_date, creation_date)) desc

Or a case expression:

order by (case when change_date > creation_date then change_date
               else creation_date
          end)

Answer 2

There's no compare , but - use greatest .

order by greatest(creation_date, change_date) desc

Answer 3

Do you mean this? You can order by Boolean expressions...

WITH
indata(comp,cr_dt,chg_dt) AS (
          SELECT 'same'      ,'2021-02-15', '2021-02-15' FROM dual
UNION ALL SELECT 'cr_bigger' ,'2021-02-16', '2021-02-15' FROM dual
UNION ALL SELECT 'chg_bigger','2021-02-15', '2021-02-16' FROM dual
UNION ALL SELECT 'cr_bigger' ,'2021-02-26', '2021-02-25' FROM dual
UNION ALL SELECT 'chg_bigger','2021-02-25', '2021-02-26' FROM dual
)
SELECT
  CASE WHEN cr_dt > chg_dt
    THEN 1
    ELSE 0
  END AS cr_is_greater
, comp
, cr_dt
, chg_dt
FROM indata
ORDER BY 1 DESC
;
 cr_is_greater |    comp    |   cr_dt    |   chg_dt
---------------+------------+------------+------------
             1 | cr_bigger  | 2021-02-16 | 2021-02-15
             1 | cr_bigger  | 2021-02-26 | 2021-02-25
             0 | same       | 2021-02-15 | 2021-02-15
             0 | chg_bigger | 2021-02-15 | 2021-02-16
             0 | chg_bigger | 2021-02-25 | 2021-02-26