Procedure Overloading Restrictions

PL/SQL lets you overload subprogram names. That is, you can use the same name for several different subprograms as long as their formal parameters differ in number, order, or datatype family. 

 

 Restrictions

Only local or packaged subprograms can be overloaded. Therefore, you cannot overload standalone subprograms. Also, you cannot overload two subprograms if their formal parameters differ only in name or parameter mode. For example, you cannot overload the following two procedures:

PROCEDURE reconcile (acctno IN INTEGER) IS

BEGIN

...

END;

PROCEDURE reconcile (acctno OUT INTEGER) IS

BEGIN

...

END;

Furthermore, you cannot overload two subprograms if their formal parameters differ only in datatype and the different datatypes are in the same family. For instance, you cannot overload the following procedures because the datatypes INTEGER and REAL are in the same family:

PROCEDURE charge_back (amount INTEGER) IS

BEGIN

...

END;

PROCEDURE charge_back (amount REAL) IS

BEGIN

...

END;

Likewise, you cannot overload two subprograms if their formal parameters differ only in subtype and the different subtypes are based on types in the same family. For example, you cannot overload the following procedures because the base types CHAR and LONG are in the same family:

DECLARE

SUBTYPE Delimiter IS CHAR;

SUBTYPE Text IS LONG;

...

PROCEDURE scan (x Delimiter) IS

BEGIN ... END;

PROCEDURE scan (x Text) IS

BEGIN ... END;

Finally, you cannot overload two functions that differ only in return type (the datatype of the result value) even if the types are in different families. For example, you cannot overload the following functions:

FUNCTION acct_ok (acct_id INTEGER) RETURN BOOLEAN IS

BEGIN ... END;

FUNCTION acct_ok (acct_id INTEGER) RETURN INTEGER IS

BEGIN ... END;