Oracle SQL voorwaardelijke rangschikking

Als ik het goed begrijp, kun je proberen CASE WHEN . te gebruiken met sum vensterfunctie

CASE WHEN controleer col3 is niet null accumuleren anders toon NULL

CREATE TABLE T(
  col1 VARCHAR(5),
  col2 DATE,
  col3 DATE
);

INSERT INTO T VALUES ( 'a' , to_date('2018-01-20','YYYY-MM-DD') , to_date('2018-03-04','YYYY-MM-DD'));  
INSERT INTO T VALUES ( 'a' , to_date('2018-01-24','YYYY-MM-DD') , to_date('2018-04-04','YYYY-MM-DD'));  
INSERT INTO T VALUES ( 'b' , to_date('2018-01-02','YYYY-MM-DD') , to_date('2018-05-03','YYYY-MM-DD'));  
INSERT INTO T VALUES ( 'c' , to_date('2017-01-02','YYYY-MM-DD') , to_date('2017-05-08','YYYY-MM-DD'));  
INSERT INTO T VALUES ( 'd' , TO_DATE('2016-05-24','YYYY-MM-DD') , null);  
INSERT INTO T VALUES ( 'c' , TO_DATE('2018-02-05','YYYY-MM-DD') , to_date('2018-05-03','YYYY-MM-DD'));  
INSERT INTO T VALUES ( 'c' , TO_DATE('2018-07-28','YYYY-MM-DD') , null);  

Query 1 :

select t1.*,
    rank() OVER(partition by col1 order by col2 desc) rank1,
    (CASE WHEN COL3 IS NOT NULL THEN
       SUM(CASE WHEN COL3 IS NOT NULL THEN 1 ELSE 0 END) OVER(partition by col1 order by col2 desc)
    ELSE
       NULL
    END) rank2
FROM T t1

Resultaten :

| COL1 |                 COL2 |                 COL3 | RANK1 |  RANK2 |
|------|----------------------|----------------------|-------|--------|
|    a | 2018-01-24T00:00:00Z | 2018-04-04T00:00:00Z |     1 |      1 |
|    a | 2018-01-20T00:00:00Z | 2018-03-04T00:00:00Z |     2 |      2 |
|    b | 2018-01-02T00:00:00Z | 2018-05-03T00:00:00Z |     1 |      1 |
|    c | 2018-07-28T00:00:00Z |               (null) |     1 | (null) |
|    c | 2018-02-05T00:00:00Z | 2018-05-03T00:00:00Z |     2 |      1 |
|    c | 2017-01-02T00:00:00Z | 2017-05-08T00:00:00Z |     3 |      2 |
|    d | 2016-05-24T00:00:00Z |               (null) |     1 | (null) |