Functions
- 2. Function and Procedure Parameter Types Named PL/SQL programs (Procedures and Functions) can take parameters. Parameters are optional on both procedures and functions. Keep the parameter name under 30 characters, they must start with a letter and contain no spaces. There are 3 types of parameter- IN, OUT and IN OUT 2
- 3. Function and Procedure Parameter Types Cont… An IN parameter is used as an input only. An IN parameter cannot be changed by the called program. An OUT parameter is initially NULL. The program assigns the parameter a value and that value is returned to the calling program. An IN OUT parameter may or may not have an initial value. That initial value may or may not be modified by the called program. Any changes made to the parameter are returned to the calling program. 3
- 4. Function and Procedure Parameter Types Cont… Parameters are declared with data types but without data type length or precision. A parameter may be declared as VARCHAR2 but it will not be declared with a length component (VARCHAR2(30) would not be valid). Parameters may also be assigned a default value. You can either use the assignment operator (:=) or use the DEFAULT keyword. When a parameter has a default value, you do not need to include that parameter in the call. 4
- 5. Sample Parameter Declarations ( parameter_1 IN VARCHAR2 := 'ABC', parameter_2 IN VARCHAR2 DEFAULT 'ABC', parameter_3 IN OUT NUMBER, parameters_can_be_named_anything OUT DATE ) 5
- 6. Procedure Example CREATE OR REPLACE PROCEDURE my_first_proc (p_name IN VARCHAR2 := 'Lewis', p_address IN VARCHAR2 := '123 Mockingbird Ln', p_an_in_out_parameter IN OUT NUMBER, p_an_out_parameter OUT DATE ) IS v_a_variable VARCHAR2(30); BEGIN IF p_name = 'Lewis' THEN DBMS_OUTPUT.PUT_LINE( p_name || ': ' || p_address ); END IF; v_a_variable := 99; p_an_in_out_parameter := v_a_variable; p_an_out_parameter := SYSDATE; END; 6
- 7. Function Example CREATE OR REPLACE FUNCTION my_first_func (p_name IN VARCHAR2 := 'Lewis', p_address IN VARCHAR2 := '123 Mockingbird Ln', p_an_in_out_parameter IN OUT NUMBER, p_an_out_parameter OUT DATE ) RETURN VARCHAR2 IS v_a_variable VARCHAR2(30); BEGIN IF p_name = 'Lewis' THEN RETURN -1; END IF; v_a_variable := 99; p_an_in_out_parameter := v_a_variable; p_an_out_parameter := SYSDATE; RETURN v_a_variable; END; 7
- 8. Procedures VS Functions Procedures are traditionally the workhorse of the coding world. Functions are traditionally the smaller, more specific pieces of code. In general, if you need to update the chart of accounts, you would write a procedure. If you need to retrieve the organization code for a particular GL account, you would write a function. A Procedure cannot return a value but a Function MUST return a value. 8
- 9. Procedures VS Functions Cont… The return statement in a function returns control to the calling program and returns the results of the function. The return statement of a procedure returns control to the calling program and cannot return a value. Functions can be called from SQL, Procedure cannot. Functions are considered expressions, Procedure are not. Procedures and functions can both return data in OUT and IN OUT parameters. 9