[sql] What's the difference between RANK() and DENSE_RANK() functions in oracle?

rank() : It is used to rank a record within a group of rows.

dense_rank() : The DENSE_RANK function acts like the RANK function except that it assigns consecutive ranks.

Query -

select 
    ENAME,SAL,RANK() over (order by SAL) RANK
from 
    EMP;

Output -

+--------+------+------+
| ENAME  | SAL  | RANK |
+--------+------+------+
| SMITH  |  800 |    1 |
| JAMES  |  950 |    2 |
| ADAMS  | 1100 |    3 |
| MARTIN | 1250 |    4 |
| WARD   | 1250 |    4 |
| TURNER | 1500 |    6 |
+--------+------+------+

Query -

select 
    ENAME,SAL,dense_rank() over (order by SAL) DEN_RANK
from 
    EMP;

Output -

+--------+------+-----------+
| ENAME  | SAL  |  DEN_RANK |
+--------+------+-----------+
| SMITH  |  800 |         1 |
| JAMES  |  950 |         2 |
| ADAMS  | 1100 |         3 |
| MARTIN | 1250 |         4 |
| WARD   | 1250 |         4 |
| TURNER | 1500 |         5 |
+--------+------+-----------+

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