What is the difference between RANK and DENSE_RANK functions in Oracle ?

In simple words both does the same except RANK skips if there is a tie and DENSE_RANK does not. So remember to use DENSE_RANK to use in Nth largest queries.

Detailed explanation of RANK and DESNSE_RANK given in another posts

RANK Function

DENSE_RANK Function

Example :-

Consider below emp table data

EMPNO	EMPNAME	SALARY	DEPTNO
10	Bill	12000	5
11	Solomon	10000	5
12	Susan	10000	5
13	Wendy	9000	1
14	Benjamin	7500	1
15	Tom	7600	1
16	Henry	8500	2
17	Robert	9500	2
18	Paul	7700	2

select empno,salary,
rank() over(order by salary asc) “rank”,
dense_rank() over(order by salary asc) “dense_rank”
from emp;

See the result

RANK function skips number 8 while DENSE_RANK does not.