Dr. James Dullea, CSC8490 Introduction to PL/SQLSlide 1 of 36 7From Prof. Dullea CSC8490...

Dr. James Dullea, CSC8490 Introduction to PL/SQL

Slide 1 of 36

7 From Prof. Dullea CSC8490

Introduction to PL/SQL

Module 01-9

Revised: June 12, 2005

Dr. James Dullea [email protected]

Dr. James Dullea, CSC8490 Introduction to PL/SQL Slide 2 of 36

Introduction to PL/SQL

What is PL/SQL Why PL/SQL Kinds of PL/SQL BLOCKS

Anonymous or Named Blocks Named Blocks (Stored procedures,

Funtions, Triggers) Exceptions Assignments (2)


What is PL/SQL

PL/SQL is a sophistical programming language used to access an Oracle database from a various environments.

PL/SQL stands for Procedural Language/SQL.It extends SQL by adding constructs found in other procedural languages, such as: loops, conditional statements, declared variables, accessing individual records one at a time, and many others.


Why use PL/SQLCompared to SQL, PL/SQL has the procedural constructs that are useful to express a desired process from start to end.

One block of PL/SQL code can bundled several SQL statements together as a single unit. Making less network traffic and improving application performance.

PL/SQL can be integrated with other languages, such as Java, to take advantage of the strongest features of both languages.


Kinds of PL/SQL BLOCKSThe basic unit in any PL/SQL PROGRAM is a BLOCK. All PL/SQL programs are composed of a single block or blocks that occur either sequentially or nested within another block. There are two kinds of blocks:

Anonymous blocks are generally constructed dynamically and executed only once by the user. It is sort of a complex SQL statement.

Named blocks are blocks that have a name associated with them, are stored in the database, and can be executed again and again, can take in parameters, and can modify and existing database.


Structure of Anonymous Block

DECLARE/* Declare section (optional). */

BEGIN/* Executable section (required). */

EXCEPTION/* Exception handling section

(optional). */

END; -- end the block (do not forget the “ ; “ in the end.)

/


Example of Anonymous BlockSET SERVEROUTPUT ONDECLARE v_last_name VARCHAR2(15); v_salary employee.salary%TYPE; CURSOR c_query IS SELECT lname, salary FROM employee; BEGIN OPEN c_query; LOOP FETCH c_query INTO v_last_name, v_salary; IF v_salary >= 40000 THEN DBMS_OUTPUT.PUT_LINE (v_last_name||' '||v_salary); END IF; EXIT WHEN c_query%NOTFOUND; END LOOP; CLOSE c_query;END; /


PL/SQL Build-In Utility PackagesDBMS_OUTPUT.PUT_LINE

SET SERVEROUTPUT ON to allow output to be displayed to the screen

DBMS_OUTPUT.PUT_LINE Usage: DBMS_OUTPUT.PUT_LINE ( Argument ) Argument tendS to resemble the

concatenated arguments of the SELECT clause in an SQL query.

If the argument is not initialized, then a NULL VALUE will be displayed.


PL/SQL Build-In Utility Packages Example

SET SERVEROUTPUT ONDECLARE v_name VARCHAR2(30); v_title VARCHAR2(20);BEGIN v_name := 'James Dullea'; v_title := 'Research Scientist'; DBMS_OUTPUT.PUT_LINE(v_name||' works as a '||

v_title);END;/


Variables and TypesA variable is a storage location that can be

read from or assigned to by the program.

It is declared in the declarative section within a PL/SQL block.

v_last_name VARCHAR2(15);

Every variable has a specific data type associated with it. Variables can be associated with a table structure.

v_salary employee.salary%TYPE;


Data TypesScalar type Numeric: INT,

DEC,NUMBER,BINARY_INTEGER…Character: CHAR, CHARACTER, STRING, VARCHAR, VARCHAR2…Boolean: TRUE, FALSE.Date: DATE

Composite types RECORD, TABLE, VARRAY

Reference types CURSORS, OBJECT TYPES

Lob types BFILE, LOB, CLOB, NLOB


CURSORS A cursor is used to process a single row

'at a time' from multiple rows retrieved from the database .

Cursors are declared in the Declaration Section.

CURSOR c_query IS SELECT lname, salary FROM employee;

The cursor can be declared for complex queries involving joins and conditions.

Cursors must be OPENed to be accessed and CLOSEd before ending the program.

OPEN c_query; CLOSE c_query;


CURSORS The FETCH statement is used to

retrieve the output of a single record from the CURSOR SELECT statement INTO associate variables.

FETCH c_query INTO v_last_name, v_salary; Cursors can be opened and closed

more than once in a block and if the a WHERE statement exists, the values of the binding variables can be modified.

“Cursor FOR loop” is a special type of for loop which the SQL cursor operations are carried out implicitly.


Conditional Statements

Conditional Processing

The specifiedconditions areevaluated by thesystem and the resultdetermines whichsequence ofstatements is to becarried out.

IF <boolean expression> THEN <sequence of statements>END IF;---------------------------------------------------------------------------------------------

IF <boolean expression> THEN <sequence of statements>ELSE<sequence of statements>END IF;


Conditional Statements (ELSIF)

IF <boolean expression> THEN <sequence of statements>ELSIF <boolean expression> THEN<sequence of statements>ELSIF <boolean expression> THEN<sequence of statements>ELSIF <boolean expression> THEN<sequence of statements>ELSE<sequence of statements>END IF;


Loop Structures

Unconstrained loops WHILE loop FOR loop GOTO <<LABEL>>


Unconstrained Loops

LOOP <sequence of

statements> EXIT WHEN

<condition><sequence of

statements> END LOOP;


WHILE LOOP

WHILE <condition> LOOP

<statements> END LOOP; Note: The loop will continue to

process as long as the condition is TRUE or an EXIT (or EXIT WHEN) statement is encountered.


FOR LOOP

FOR <loop_counter> IN [REVERSE] <low bound>..<high bound> LOOP <sequence of statements> END LOOP;


GOTO statement GOTO label;The label is defined in the block bybeing enclosed in double angle brackets.

Example:LOOP<sequence of statements>IF <condition> THENGOTO get_out_of_loop;<sequence of statements>END LOOP;<<get_out_of_loop>>


NAMED BLOCKSThe following are types of NAMED BLOCKS Stored Procedures

Similar to an anonymous block except it can be stored in the database, can accept parameters, and can be executed over and over again (with different parameters)

Functions Type of named blocks that is executed within a

DML or SQL statement. It may take in one or more parameters and RETURNs only one value back to the calling application.

TriggersA named block that executes only when an

associated DML statement is executed, such as an INSERT, UPDATE, or DELETE statement.


Block Structure for PL/SQL Subprograms (Procedures or

Functions)

Program Comments (optional) Header (mandatory) IS|AS (mandatory) Declaration Section BEGIN (mandatory) Executable Section EXCEPTION (optional) Exception Section END; (mandatory) /


Block Structure for PL/SQL subprograms

Completed procedure exampleCREATE OR REPLACE PROCEDURE AddDepartment/*Procedure to add rows In the COMPANY.department table */(p_DepartmentName IN department.dname%TYPE, p_DepartmentNumber IN department.dnumber%TYPE, p_DepartmentManager IN department.mgrssn%TYPE, p_ManagerStartDate IN department.mgrstartdate%TYPE) AS BEGININSERT INTO DEPARTMENT(dname, dnumber, mgrssn, mgrstartdate)VALUES (p_DepartmentName, p_DepartmentNumber, p_DepartmentManager,

p_ManagerStartDate);COMMIT;END AddDepartment;/


Execution of a Stored Functions

EXEC AddDepartment ('Info Center', 43, '888665555', '28-JUN-2005');


Syntax of a Stored FunctionsCREATE OR REPLACE FUNCTION function_name(parameters IN datatypes)RETURN datatype IS|AS

Declaration SectionBEGIN

Executable SectionRETURN variable_nameEXCEPTION (optional)

Exception SectionEND;


Example of a Stored Functions

Given the salary of an employee, calculate the state tax of 2.8% from the salary and return it.


Example of a Stored Functions

CREATE OR REPLACE FUNCTION CalcStateTax ( p_salary IN employee.salary%TYPE) RETURN NUMBERASBEGIN RETURN (p_salary * 0.028);END CalcStateTax;/



SELECT fname||' '||lname AS "EMPLOYEE", CalcStateTax(salary) AS "STATE TAX"FROM employee;



EMPLOYEE STATE TAX

------------------------------- ----------

James Borg 1540

Jennifer Wallace 1204

Franklin Wong 1120

John Smith 840

Alicia Zelaya 700

Ramesh Narayan 1064

Joyce English 700

Ahmad Jabbar 700

8 rows selected.


What is a TriggerSimilar to stored procedures and functions. Contains a Declaration, Executable, and

Exception sectionsDifferences Triggers are not executed explicitly, they are

implicitly execute when a triggering event occurs. (This is called firing the trigger)

Triggers do not accept parameters Triggering events are fired by DML

Statements ( INSERTs, UPDATEs, or DELETEs) against tables or views AND certain system events


Why Use Triggers Complex integrity constraints are not

always possible through declarative constraints enabled at table creation time, such as salary may not be lowered.

Auditing information, such as who updated an employee's salary, may be required. Remember triggers happen at the basic DML level.

Triggers can signal other application that action needs to take place when changes are made to a table. Example, update employee statistics contained in another table.


Block Structure for a PL/SQL Trigger

CREATE [OR REPLACE] TRIGGER trigger_nameAFTER | BEFORE | INSTEAD OF a_trigger_eventON table_name (or view_name) [FOR EACH ROW[WHEN trigger_condition]]DECLARE (optional)BEGIN (mandatory)

Executes only when trigger_condition is TRUE on a ROW LEVEL TRIGGER

EXCEPTION (optional)Exception Section

END; (mandatory) NOTE: a_trigger_event may be any combination of

an INSERT, DELETE, and/or UPDATE on a table or view


Errors and Error Handling Errors can be classified into two types:

1) Compile-Time errors and warnings.

After compiling use the command

SHOW ERRORS

use SET ECHO ON to see statement

numbers

2) Run-Time errors occur during execution

and throw exception that can be handled by

the program.


Error Handling

When errors occur during the execution, control will be branched to the exception handling section.

A corresponding error handler will be

found to deal with the error.


Practice 1Use the Company database schema, write a stored

procedure to add an employee to the employee table, using parameters to input the data. Use your name and following information to test the procedure.

FNAME use your first name

MINIT use your middle init or a blank space

LNAME use your last name

SSN make up a 9 digit number

BDATE use your birthday (be careful of the date format)

STREET make up data

CITY Villanova

STATE PA

ZIP use the Villanova zip code

SEX M or F

SALARY 38000

SUPERSSN 333445555

DNO 5


Practice 2Write a function (called GetDay) that will take in a

date as a parameter and return the actual name of the day for that date. Use the function to solve the following problem.

Using the data in the employee table from Assignment 1, write an SQL statement or an anonymous block (containing the above function GetDay) that uses your first and last name in a where clause to access the record and returns the actual day of the week that you were born. Hint: GetDay(bdate)

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