Oracle sql KEEP clause

Oracle sql KEEP clause 


select 
deptno,
min(sal) ,
min(empno) keep (dense_rank first order by sal ) empnomin,
max(sal) ,
max(empno) keep (dense_rank last order by sal ) empnomax
from emp
group by deptno;



   DEPTNO   MIN(SAL)   EMPNOMIN   MAX(SAL)   EMPNOMAX
---------- ---------- ---------- ---------- ----------
        10       1300       7934       5000       7839
        20        800       7369       3000       7902
        30        950       7900       2850       7698


====================

select * from emp

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

14 rows selected.






CREATE TABLE dense_rank_demo (
    col VARCHAR2(10) NOT NULL
);

INSERT ALL 
    INTO dense_rank_demo(col) VALUES('A')
    INTO dense_rank_demo(col) VALUES('A')
    INTO dense_rank_demo(col) VALUES('B')
    INTO dense_rank_demo(col) VALUES('C')
    INTO dense_rank_demo(col) VALUES('C')
    INTO dense_rank_demo(col) VALUES('C')
    INTO dense_rank_demo(col) VALUES('D')
SELECT 1 FROM dual; 

commit ;



SQL> select * from dense_rank_demo;

COL
----------
A
A
B
C
C
C
D




SELECT
	col,
	DENSE_RANK () OVER ( 
		ORDER BY col ) 
	rank
FROM
	dense_rank_demo;



COL              RANK
---------- ----------
A                   1
A                   1
B                   2
C                   3
C                   3
C                   3
D                   4

7 rows selected.