NVL and NVL2 functions

NVL

Syntax: NVL(expr1,expr2)

NVL lets you replace null (returned as a blank) with a string in the results of a query. If expr1 is null, then NVL returns expr2. If expr1 is not null, then NVLreturns expr1.

The arguments expr1 and expr2 can have any data type. If their data types are different, then Oracle Database implicitly converts one to the other. If they cannot be converted implicitly, then the database returns an error. The implicit conversion is implemented as follows:

• If expr1 is character data, then Oracle Database converts expr2 to the data type of expr1 before comparing them and returns VARCHAR2 in the character set of expr1. 

• If expr1 is numeric, then Oracle Database determines which argument has the highest numeric precedence, implicitly converts the other argument to that data type, and returns that data type.

NVL2

Syntax: NVL2(expr1,expr2,exp3)

NVL2 lets you determine the value returned by a query based on whether a specified expression is null or not null. If expr1 is not null, then NVL2 returnsexpr2. If expr1 is null, then NVL2 returns expr3.

The argument expr1 can have any data type. The arguments expr2 and expr3 can have any data types except LONG.

If the data types of expr2 and expr3 are different, then Oracle Database implicitly converts one to the other. If they cannot be converted implicitly, then the database returns an error. If expr2 is character or numeric data, then the implicit conversion is implemented as follows:

• If expr2 is character data, then Oracle Database converts expr3 to the data type of expr2 before returning a value unless expr3 is a null constant. In that case, a data type conversion is not necessary, and the database returns VARCHAR2 in the character set of expr2. 

• If expr2 is numeric data, then Oracle Database determines which argument has the highest numeric precedence, implicitly converts the other argument to that data type, and returns that data type.