Function Expressions

You can use any built-in SQL function or user-defined function as an expression. Some valid built-in function expressions are:

LENGTH('BLAKE') 
ROUND(1234.567*43) 
SYSDATE

See Also:

"SQL Functions" and "Aggregate Functions" for information on built-in functions

A user-defined function expression specifies a call to:

A function in an Oracle-supplied package (see PL/SQL Packages and Types Reference)
A function in a user-defined package or type or in a standalone user-defined function (see "User-Defined Functions")
A user-defined function or operator (see CREATE OPERATOR, CREATE FUNCTION, and Oracle Data Cartridge Developer's Guide)

Some valid user-defined function expressions are:

circle_area(radius)
payroll.tax_rate(empno)
hr.employees.comm_pct(dependents, empno)@remote
DBMS_LOB.getlength(column_name)
my_function(DISTINCT a_column)

Restriction on User-Defined Function Expressions You cannot pass arguments of object type or XMLType to remote functions and procedures.