Advanced Oracle PL/SQL Developer's Guide - Second Edition

Functions

Similar to a stored procedure, a function is a named derivative of a PL/SQL block that is physically stored within the Oracle database schema.

The key features of stored functions are as follows:

• A function can accept parameters in all three modes (IN, OUT, and IN OUT) and mandatorily returns a value.
• Functions can be called in SQL statements (SELECT and DMLs). Such functions must accept only IN parameters of valid SQL types. Alternatively, a function can also be invoked from SELECT statements if the function body obeys the database purity rules.
• If the function is called from an SQL statement, its return type should be a valid SQL data type. If the function is invoked from PL/SQL, the return type should be a valid PL/SQL type.

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