无法按数据分组

聚合函数忽略空值,因此需要 anaytic version :

select a, b, min(date_) keep (dense_rank first order by date_ nulls first) 
  from input group by a, b

^demo

Oracle设置 :

CREATE TABLE table_name ( A, B, DT ) AS
SELECT 0, 12, DATE '2019-01-22' FROM DUAL UNION ALL
SELECT 0, 12, NULL FROM DUAL UNION ALL
SELECT 0, 25, DATE '2019-01-22' FROM DUAL UNION ALL
SELECT 0, 24, DATE '2019-01-22' FROM DUAL;

查询 :

SELECT A,
       B,
       CASE
       WHEN COUNT( CASE WHEN DT IS NULL THEN 1 END ) > 0
       THEN NULL
       ELSE MAX( DT )
       END AS DT
FROM   table_name
GROUP BY A, B;

产量 :

 A |  B | DT       
-: | -: | :--------
 0 | 12 | null     
 0 | 24 | 22-JAN-19
 0 | 25 | 22-JAN-19

小提琴 here