NULLIF:
Syntax: NULLIF(expr1, expr2)
Description: Compares expr1 and expr2. If they are equal, then the function returns null. If they are not equal, then the function returns expr1.
Example: NULLIF({price}, 0)
NVL:
Syntax: NVL(expr1, expr2)
Description: Lets you replace null with the second parameter.
Example: NVL({quantity},’0′)
NVL2:
Syntax: NVL2(expr1, expr2, expr3)
Description: If expr1 is not null, then NVL2 returns expr2. If expr1 is null, then NVL2 returns expr3.
Example: NVL2({location}, 1, 2)