Choice functions

Choice functions provide a way to select from two values based on some characteristic of one of the values.

Function	Definition	Datatype constraint
COALESCE(x,y+)	Returns the first non-null parameter.	x and all y’s can be any compatible types.
IFNULL(x,y)	If x is null, return y; else return x.	x, y, and the return type must be the same type but can be any type.
NVL(x,y)	If x is null, return y; else return x.	x, y, and the return type must be the same type but can be any type.
NULLIF(param1, param2)	Equivalent to case when (param1 = param2) then null else param1.	param1 and param2 must be compatable comparable types.

Function

Definition

Datatype constraint

COALESCE(x,y+)

Returns the first non-null parameter.

x and all y’s can be any compatible types.

IFNULL(x,y)

If x is null, return y; else return x.

x, y, and the return type must be the same type but can be any type.

NVL(x,y)

If x is null, return y; else return x.

x, y, and the return type must be the same type but can be any type.

NULLIF(param1, param2)

Equivalent to case when (param1 = param2) then null else param1.

param1 and param2 must be compatable comparable types.

IFNULL and NVL are aliases of each other. They are the same function.

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