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From Prof. Dullea CSC8490 Introduction to PL/SQL

From Prof. Dullea CSC8490 Introduction to PL/SQL. Dr. James Dullea professor@comcast.net . Module 01-9 Revised: June 12, 2005. Introduction to PL/SQL. What is PL/SQL Why PL/SQL Kinds of PL/SQL BLOCKS Anonymous or Named Blocks

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From Prof. Dullea CSC8490 Introduction to PL/SQL

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  1. From Prof. DulleaCSC8490 Introduction to PL/SQL Dr. James Dullea professor@comcast.net Module 01-9 Revised: June 12, 2005 Dr. James Dullea, CSC8490 Introduction to PL/SQL

  2. 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) Dr. James Dullea, CSC8490 Introduction to PL/SQL

  3. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  4. Why use PL/SQL Compared 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 togetheras 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  5. Kinds of PL/SQL BLOCKS The 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 blocksare 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  6. 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.) / Dr. James Dullea, CSC8490 Introduction to PL/SQL

  7. Example of Anonymous Block SET SERVEROUTPUT ON DECLARE 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; / Dr. James Dullea, CSC8490 Introduction to PL/SQL

  8. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  9. PL/SQL Build-In Utility PackagesExample SET SERVEROUTPUT ON DECLARE 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; / Dr. James Dullea, CSC8490 Introduction to PL/SQL

  10. Variables and Types A 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; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  11. Data Types Dr. James Dullea, CSC8490 Introduction to PL/SQL

  12. 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; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  13. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  14. Conditional Processing The specified conditions are evaluated by the system and the result determines which sequence of statements is to be carried 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 Dr. James Dullea, CSC8490 Introduction to PL/SQL

  15. 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; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  16. Loop Structures • Unconstrained loops • WHILE loop • FOR loop • GOTO <<LABEL>> Dr. James Dullea, CSC8490 Introduction to PL/SQL

  17. Unconstrained Loops LOOP <sequence of statements> EXIT WHEN <condition> <sequence of statements> END LOOP; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  18. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  19. FOR LOOP FOR <loop_counter> IN [REVERSE] <low bound>..<high bound> LOOP <sequence of statements> END LOOP; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  20. GOTO statement GOTO label; The label is defined in the block by being enclosed in double angle brackets. Example: LOOP <sequence of statements> IF <condition> THEN GOTO get_out_of_loop; <sequence of statements> END LOOP; <<get_out_of_loop>> Dr. James Dullea, CSC8490 Introduction to PL/SQL

  21. NAMED BLOCKS The 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. • Triggers A named block that executes only when an associated DML statement is executed, such as an INSERT, UPDATE, or DELETE statement. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  22. 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) / Dr. James Dullea, CSC8490 Introduction to PL/SQL

  23. Block Structure for PL/SQL subprogramsCompleted procedure example CREATE 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 BEGIN INSERT INTO DEPARTMENT(dname, dnumber, mgrssn, mgrstartdate) VALUES (p_DepartmentName, p_DepartmentNumber, p_DepartmentManager, p_ManagerStartDate); COMMIT; END AddDepartment; / Dr. James Dullea, CSC8490 Introduction to PL/SQL

  24. Execution of a Stored Functions EXEC AddDepartment ('Info Center', 43, '888665555', '28-JUN-2005'); Dr. James Dullea, CSC8490 Introduction to PL/SQL

  25. Syntax of a Stored Functions CREATE OR REPLACE FUNCTION function_name (parameters IN datatypes) RETURNdatatype IS|AS Declaration Section BEGIN Executable Section RETURN variable_name EXCEPTION (optional) Exception Section END; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  26. Example of a Stored Functions Given the salary of an employee, calculate the state tax of 2.8% from the salary and return it. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  27. Example of a Stored Functions CREATE OR REPLACE FUNCTION CalcStateTax ( p_salary IN employee.salary%TYPE) RETURN NUMBER AS BEGIN RETURN (p_salary * 0.028); END CalcStateTax; / Dr. James Dullea, CSC8490 Introduction to PL/SQL

  28. Execution of a Stored Functions SELECT fname||' '||lname AS "EMPLOYEE", CalcStateTax(salary) AS "STATE TAX" FROM employee; Dr. James Dullea, CSC8490 Introduction to PL/SQL

  29. Execution of a Stored Functions 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  30. What is a Trigger Similar to stored procedures and functions. • Contains a Declaration, Executable, and Exception sections Differences • 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 Dr. James Dullea, CSC8490 Introduction to PL/SQL

  31. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  32. Block Structure for a PL/SQL Trigger CREATE [OR REPLACE] TRIGGER trigger_name AFTER | BEFORE | INSTEAD OF a_trigger_event ON 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 Dr. James Dullea, CSC8490 Introduction to PL/SQL

  33. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  34. 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. Dr. James Dullea, CSC8490 Introduction to PL/SQL

  35. Practice 1 Use 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 Dr. James Dullea, CSC8490 Introduction to PL/SQL

  36. Practice 2 Write 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) Dr. James Dullea, CSC8490 Introduction to PL/SQL

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