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Overloading oracle functions and stored procedures

Oracle Database Tips by Donald BurlesonJune 15, 2015

Question:  What does it mean to "overload" an Oracle stored procedure or function?  I hear that overloading has to do with what parameters are passed to the PL/SQL, but I was hoping for clarification into the nature of PL/SQL overloading.

Answer:  The process of "overloading" originates in the world of object-oriented coding with the concept of polymorphism.  It is the idea that the functionality of a PL/SQL stored procedure of function can be changed based on the input datatype.

Polymorphism was a spin off of the PL/SQL concept called "overloading"  Overloading a stored procedure or function refers to the ability of a programming method to perform more than one kind of operation depending upon the context in which the method is used. 

For a simple example of overloading, you can write a PL/SQL function that does one thing when a numeric argument is passed to the procedure and another thing when a character string is passed as an argument.

For a simple Oracle example of overloading, consider the wwv_flow_mail.send procedure.  There are two overloaded versions of the send procedure and Oracle knows which to invoke by the argument data types passed to the send procedure.  If you pass a CLOB datatype for p_body and p_body_html, then the second send procedure is invoked.

Polymorphism and overloading in PL/SQL

Polymorphism is the ability of different objects to receive the same message and respond in different ways.  Polymorphism simplifies the communication between objects by using a common interface to hide different implementation details. 

A very simple example of this is the use of the operator "+", in working with characters it can be used for concatenation and if used with numerical values it would be used for addition.  A programming example of overloading would look as follows. 

Concatenation example:

First_Name = "John"
Last_Name = "Smith"
Full_Name = First_Name + Last_Name


Numerical example

Kounter = Kounter + 1

Oracle member methods and overloading

Overloading is associated with the object-oriented idea of "polymorphism" whereby a single procedure may be context-sensitive, depending on the input parameters and it is also used in the object-oriented Oracle with the idea of member methods.

An example of this type of method would be an update method that updates a table attribute based on the value that is passed. If a date value is passed, the procedure will do the conversion to character, same with a number.
 
The technique for overloading a method procedure or function is identical to the overloading of standard procedure or function.

create type
   test3(
   type_passed varchar2(8),

   member procedure input_type(in_char char),
   member procedure input_type(in_varchar varchar2),
   member procedure input_type(in_date date),
   member procedure input_type(in_number number)
);

Click HERE for more information on Oracle stored procedures.

 
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