MOD function returns the remainder of a number divided by another number.

Syntax:

select MOD(m,n) from dual;

It is the mathematical expression m MOD n.

m MOD n returns remainder of m divided by n.

Mathematical Explanation :-

m ≡ b  (mod n)  means (m – b) is divisible by n where b is an integer.

12 ≡  2 (mod 5) means (12 -2) is divisible by 5. ie 10 is divisible by 5.

12 ≡ 0 ( mod 12) means (12 – 0) is divisible by 12.

Examples :-

1) select MOD(10,3) from dual;

MOD(10,3)
—————
1

2) select MOD(3,0) from dual;

MOD(3,0)
—————
3

2) select MOD(3,5) from dual;

MOD(3,5)
—————
3

Some more examples

MOD(5,2)	1
MOD(5,0)	5
MOD(5,5)	0
MOD(2,5)	2
MOD(-2,5)	-2
MOD(5,-1)	1
MOD(5,0.5)	0
MOD(5,1.2)	0.2

Oracle has introduced another function REMAINDER in 10g version. Note that MOD and REMAINDER function looks similar but not exactly. Explained in another post.