You can execute a procedure or function interactively using an Oracle tool, such as SQL*Plus, or call it explicitly in the code of a database
application, such as an Oracle Forms or Precompiler application, or in the code of another procedure or trigger.

creating Functions in PL/SQL

syntax is

CREATE [OR REPLACE ] FUNCTION function_name
[(Formal parameter1 [MODE] Data_type,
(Formal parameter2 [MODE] Data_type,
…..)] RETURN data_type
IS | AS

BEGIN

PL/SQL Block

RETURN return_variable;

END;

Where

Modes

MODE can be IN,OUT or IN OUT.However as per the standard,functions avoid using OUT and IN OUT parameters.The explicit return

of values is done through return statements and not through out parameters.Function should return a value to the calling phase.

Return Statment

RETURN data_type
>>Only type has to be specified and size specification is not allowed
>>Can be Scalar data type or composite datatype
>>Can Return only one value
>>should have only one return statment in the PL/SQL block

Example

CREATE OR REPLACE FUNCTION get_sal_emp(v_emp_id IN number)
RETURN number
IS
v_emp_sal number;
BEGIN

SELECT emp_sal into v_emp_sal
FROM emp WHERE emp_id=v_emp_id;

RETURN v_emp_sal;

END;

Invoking the Function

SQL:>execute:salary:=get_sal_emp(182312);

Removing the Function

DROP FUNCTION function_name;

example

DROP FUNCTION get_emp_sal;

It will remove the stored function get_emp_sal
It also remove the related data dictionary entries and contents