Oracle : How to write a SQL query to show serial numbers for each set of same values ? : For example if I have a table like 
EmpID , Empname , Country 

Output should be like 

EmpId	EmpName	Country	Serial No.
1	ABC	India	    1
2	BCD	India	    2
3	CMO	India	    3
4	DIS	China	    1
5	FGH	China	    2
6	FHI	Singapore	1
7	XYZ	Singapore	2
8	KLM	Singapore	3
9	NOP	Singapore	4
10	QRS	Singapore	5

Here Group by Value is Country. 
