如果第一个条件满足执行它，否则在 Oracle 中的第二个条件

Question

I am trying to take Employee by status from table. I have 2 statuses, If an employee has A condition take that row, otherwise take P status row with maximum oper_day It looks like below:

Table

---------------------------------------------------
id  |  emp_code  | name    | status   | oper_day  |
--------------------------------------------------
1   |  164094    | John    | P        | 2020-10-02 |
2   |  164094    | John    | P        | 2020-10-09 |
3   |  164094    | John    | A        | 2020-10-10 |
4   |  145890    | Mike    | P        | 2020-10-05 |

My result should look like below

--------------------------------
id  |  emp_code  | name    | status   | oper_day  |
--------------------------------------------------
1   |  164094    | John    | A        | 2020-10-10 |
2   |  145890    | Mike    | P        | 2020-10-05 |

Any help is appreciated

Answer 1

Using ROW_NUMBER :

WITH cte AS (
    SELECT t.*, ROW_NUMBER() OVER (PARTITION BY emp_code ORDER BY status, oper_day DESC) rn
    FROM yourTable t
)

SELECT id, emp_code, name, status, oper_day  
FROM cte
WHERE rn = 1;

The logic here is that should an employee have a status A record, it would be assigned the first row number, since A sorts before P . Otherwise, a P status record would be chosen. We choose the more recent record per employee in case of multiple records.

Answer 2

You can use aggregation functions with KEEP( DENSE_RANK FIRST ORDER BY ... ) :

SELECT MAX( id ) KEEP ( DENSE_RANK FIRST ORDER BY status ASC, oper_day DESC ) AS id,
       emp_code,
       MAX( name ),
       MIN( status ) AS status,
       MAX( oper_day ) KEEP ( DENSE_RANK FIRST ORDER BY status ) AS oper_day
FROM   table_name
GROUP BY
       emp_code

Which., for your sample data:

CREATE TABLE table_name ( id, emp_code, name, status, oper_day ) AS
SELECT 1, 164094, 'John', 'P', DATE '2020-10-02' FROM DUAL UNION ALL
SELECT 2, 164094, 'John', 'P', DATE '2020-10-09' FROM DUAL UNION ALL
SELECT 3, 164094, 'John', 'A', DATE '2020-10-10' FROM DUAL UNION ALL
SELECT 4, 145890, 'Mike', 'P', DATE '2020-10-05' FROM DUAL;

Outputs:

\nID | EMP_CODE |  MAX(NAME) |  STATUS | OPER_DAY            \n-: |  -------: |  :-------- |  :----- |  :------------------ \n 4 |  145890 |  Mike | P |  2020-10-05 00:00:00 \n 3 |  164094 |  John | A | 2020-10-10 00:00:00 \n

db<>fiddle here