Advanced Databases Advanced PL/SQL Programming: Procedure, Function and Package

Anonymous PL/SQL Programs Write code in text editor, execute it in SQL*Plus Code can be stored as text in file system Program cannot be called by other programs, or executed by other users Cannot accept or pass parameter values

Named PL/SQL Programs Can be created: –Using text editor & executed in SQL*Plus –Using Procedure Builder Can be stored: –As compiled objects in database –As source code libraries in file system Can be called by other programs Can be executed by other users

Named Program Locations Server-side –Stored in database as database objects –Execute on the database server Client-side –Stored in the client workstation file system –Execute on the client workstation

Named Program Types Program Units (client or server-side) –Procedures –Functions Libraries (client-side) Packages (client or server-side) Triggers (server-side)

Program Units Procedures –Can receive and pass multiple parameter values –Can call other program units Functions –Like procedures, except they return a single value

 Variables used to pass data values in/out of program units  Declared in the procedure header  Parameter values are passed when the procedure is called from the calling program Parameters

Parameter Modes IN –Incoming values, read-only (default) OUT –Outgoing values, write-only IN OUT –Can be both incoming and outgoing

Creating a Procedure CREATE OR REPLACE PROCEDURE procedure_name (parameter1 mode datatype, parameter2 mode datatype, … ) IS | AS local variable declarations BEGIN program statements EXCEPTION exception handlers END; header body

Executing a Procedure EXECUTE procedure_name (parameter1_value, parameter2_value, …);

 Formal parameters: declared in procedure header  Actual parameters: values placed in parameter list when procedure is called  Values correspond based on order Procedure Header: PROCEDURE calc_gpa (s_id IN NUMBER, term_id IN NUMBER, gpa OUT NUMBER); Procedure Call: calc_gpa (current_s_id, 4, current_gpa); Parameter Types Formal Parameters Actual Parameters

Dropping A Procedure DROP PROCEDURE proc_name

Creating a Function CREATE OR REPLACE FUNCTION function_name (parameter1 mode datatype, parameter2 mode datatype, … ) RETURN function_return_data_type IS local variable declarations BEGIN program statements RETURN return_value; EXCEPTION exception handlers RETURN EXCEPTION_NOTICE; END; header body

Function Syntax Details RETURN command in header specifies data type of value the function will return RETURN command in body specifies actual value returned by function

Calling a Function Can be called from either named or anonymous PL/SQL blocks Can be called within SQL queries return_value := function_name(parameter1_value, parameter2_value, …);

Stored Program Unit Object Privileges Stored program units exist as objects in your database schema To allow other users to use your units, you must grant them EXECUTE privileges GRANT EXECUTE ON unit_name TO username;

Using Stored Program Units That Belong to Other Users You must have been granted the privilege to use it You must preface the unit name with the owner’s username return_value := LHOWARD.my_function TO_DATE(’07/14/1958’, ‘MM/DD/YYYY’);

Calling Procedures From Other Procedures Use procedure name followed by parameter list procedure_name (parameter1_value, parameter2_value, …);

Create or replace PROCEDURE Get_emp_names (Dept_num IN NUMBER) IS Emp_name VARCHAR2(30); CURSOR c1 (Depno NUMBER) IS SELECT Empname FROM Emp WHERE deptno = Depno;BEGIN OPEN c1(Dept_num); LOOP FETCH c1 INTO Emp_name; EXIT WHEN C1%NOTFOUND; DBMS_OUTPUT.PUT_LINE(Emp_name); END LOOP; CLOSE c1; END; Example// Procedure that prints all employees for a given department number

Example// Function that returns the monthly salary for an employee CREATE OR REPLACE FUNCTION MYFUNC1 (emp_no integer) RETURN NUMBER IS Monthly_sal NUMBER(10,2); BEGIN SELECT round (annsalary/12) INTO Monthly_sal FROM Emp WHERE empno = emp_no; RETURN (Monthly_sal); END MYFUNC1; /

Packages Server-side code library Can contain: –Global variable declarations –Cursors –Procedures –Functions

Package Components Specification –Used to declare all public variables, cursors, procedures, functions Body –Contains underlying code for procedures and functions Rationale: –Specification is visible to users, gives details on how to use –Body is not visible, users don’t care about details

Creating a Package Specification in SQL*Plus CREATE OR REPLACE PACKAGE package_name IS --public variables variable_name datatype; --program units PROCEDURE procedure_name (parameter_list); FUNCTION function_name (parameter_list); END;

Creating a Package Specification in SQL*Plus

Creating a Package Body in SQL*Plus CREATE OR REPLACE PACKAGE BODY package_name IS private variable declarations program unit blocks END;

Creating a Package Body in SQL*Plus

Calling a Program Unit That Is In a Package Preface the program unit name with the package name PACKAGE_NAME.program_unit_name(parameter_list); Example: DBMS_OUTPUT.PUT_LINE(‘Hello World’);

Overloading Program Units in Packages Overloading –Multiple program units have the same name, but accept different input parameters Allows user to use the same command to perform an action but pass different parameter values

Package Specification With Overloaded Procedures