RANK and DENSE_RANK in Oracle

SQL> 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 09-DEC-82       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 12-JAN-83       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.

SQL> SELECT EMPNO,ENAME,DEPTNO,SAL,
  2  RANK()OVER(ORDER BY SAL) AS RANK,
  3  DENSE_RANK()OVER(ORDER BY SAL) AS DENSE_RANK
  4  FROM EMP;

     EMPNO ENAME          DEPTNO        SAL       RANK DENSE_RANK
---------- ---------- ---------- ---------- ---------- ----------
      7369 SMITH              20        800          1          1
      7900 JAMES              30        950          2          2
      7876 ADAMS              20       1100          3          3
      7521 WARD               30       1250          4          4
      7654 MARTIN             30       1250          4          4
      7934 MILLER             10       1300          6          5
      7844 TURNER             30       1500          7          6
      7499 ALLEN              30       1600          8          7
      7782 CLARK              10       2450          9          8
      7698 BLAKE              30       2850         10          9
      7566 JONES              20       2975         11         10
      7788 SCOTT              20       3000         12         11
      7902 FORD               20       3000         12         11
      7839 KING               10       5000         14         12

14 rows selected.

SQL> SELECT EMPNO,ENAME,DEPTNO,SAL,
  2  RANK()OVER(PARTITION BY DEPTNO ORDER BY SAL) AS RANK,
  3  DENSE_RANK()OVER(PARTITION BY DEPTNO ORDER BY SAL) AS DENSE_RANK
  4  FROM EMP ORDER BY DEPTNO;

     EMPNO ENAME          DEPTNO        SAL       RANK DENSE_RANK
---------- ---------- ---------- ---------- ---------- ----------
      7934 MILLER             10       1300          1          1
      7782 CLARK              10       2450          2          2
      7839 KING               10       5000          3          3
      7369 SMITH              20        800          1          1
      7876 ADAMS              20       1100          2          2
      7566 JONES              20       2975          3          3
      7788 SCOTT              20       3000          4          4
      7902 FORD               20       3000          4          4
      7900 JAMES              30        950          1          1
      7654 MARTIN             30       1250          2          2
      7521 WARD               30       1250          2          2
      7844 TURNER             30       1500          4          3
      7499 ALLEN              30       1600          5          4
      7698 BLAKE              30       2850          6          5

14 rows selected.

SQL> SELECT EMPNO,ENAME,DEPTNO,SAL,DENSE_RANK()OVER(ORDER BY SAL DESC) AS DENSE_RANK FROM EMP;

     EMPNO ENAME          DEPTNO        SAL DENSE_RANK
---------- ---------- ---------- ---------- ----------
      7839 KING               10       5000          1
      7902 FORD               20       3000          2
      7788 SCOTT              20       3000          2
      7566 JONES              20       2975          3
      7698 BLAKE              30       2850          4
      7782 CLARK              10       2450          5
      7499 ALLEN              30       1600          6
      7844 TURNER             30       1500          7
      7934 MILLER             10       1300          8
      7521 WARD               30       1250          9
      7654 MARTIN             30       1250          9
      7876 ADAMS              20       1100         10
      7900 JAMES              30        950         11
      7369 SMITH              20        800         12

14 rows selected.

SQL> SELECT * FROM (
  2  SELECT EMPNO,ENAME,DEPTNO,SAL,DENSE_RANK()OVER(ORDER BY SAL DESC) AS RNK FROM EMP
  3  ) WHERE RNK<=5;

     EMPNO ENAME          DEPTNO        SAL        RNK
---------- ---------- ---------- ---------- ----------
      7839 KING               10       5000          1
      7788 SCOTT              20       3000          2
      7902 FORD               20       3000          2
      7566 JONES              20       2975          3
      7698 BLAKE              30       2850          4
      7782 CLARK              10       2450          5

6 rows selected.

SQL>

Queries:

SELECT * FROM EMP;
SELECT EMPNO,ENAME,DEPTNO,SAL,
RANK()OVER(ORDER BY SAL) AS RANK,
DENSE_RANK()OVER(ORDER BY SAL) AS DENSE_RANK
FROM EMP;
SELECT EMPNO,ENAME,DEPTNO,SAL,
RANK()OVER(PARTITION BY DEPTNO ORDER BY SAL) AS RANK,
DENSE_RANK()OVER(PARTITION BY DEPTNO ORDER BY SAL) AS DENSE_RANK
FROM EMP ORDER BY DEPTNO;
SELECT EMPNO,ENAME,DEPTNO,SAL,DENSE_RANK()OVER(ORDER BY SAL DESC) AS DENSE_RANK FROM EMP;
SELECT * FROM (
SELECT EMPNO,ENAME,DEPTNO,SAL,DENSE_RANK()OVER(ORDER BY SAL DESC) AS RNK FROM EMP
) WHERE RNK<=5;