1. Database Application Development
Chapter 6
PSM (Stored Procedures)
The slides for this text are organized into chapters. This lecture covers Chapter 6.
I Foundations
•Chapter 1: Introduction
•Chapter 2: ER Model and Conceptual Design
•Chapter 3: The Relational Model and SQL DDL
•Chapter 4: Relational Algebra and Relational Calculus
•Chapter 5: SQL
II Applications
•Chapter 6: Database Application Development
•Chapter 7: Database-backed Internet Applications
III Systems
•Chapter 8: Overview of Storage and Indexing
•Chapter 9: Data Storage
•Chapter 10: Tree Indexes
•Chapter 11: Hash Indexes
IV Systems
•Chapter 12: Overview of Query Evaluation
•Chapter 13: External Sorting
•Chapter 14: Evaluation of Relational Operators: First part (joins) and second part (other operators)
•Chapter 15: A Typical Relational Optimizer
V Systems
•Chapter 16: Overview of Transaction Management
•Chapter 17: Concurrency Control
•Chapter 18: Recovery
VI Applications
•Chapter 19: Schema Refinement, Functional Dependencies, Normalization
•Chapter 20: Physical Database Design, Database Tuning
•Chapter 21: Security and Authorization
VII Advanced Topics
•Chapter 22: Parallel and Distributed Database Systems
•Chapter 23: Data Warehousing and Decision Support
•Chapter 24: Object-Database Systems
•Chapter 25: Deductive Databases
•Chapter 26: Data Mining
•Chapter 27: Information Retrieval and XML Data Management
•Chapter 28: Spatial Databases

2. Stored Procedures What is a stored procedure: Advantages:
SQL allows you to define procedures and functions and store in the DB server
Program executed through single SQL statement
Executed in process space by the database server
Advantages:
Can encapsulate application logic while staying “close” to the data (usually implies efficiency)
Reuse of application logic by different users
Avoid tuple-at-a-time return of records through cursors (as would be done by JDBC)

3. SQL/PSM Declare a stored procedure:
CREATE PROCEDURE name(p1, p2, …, pn)
local variable declarations
procedure code for body;
Declare a function:
CREATE FUNCTION name (p1, …, pn) RETURNS sqlDataType local variable declarations
function code;

4. Stored Procedures: Examples
CREATE PROCEDURE ShowNumReservations
SELECT S.sid, S.sname, COUNT(*) FROM Sailors S, Reserves R WHERE S.sid = R.sid GROUP BY S.sid, S.sname;

5. Stored Procedures: Examples
Stored procedures can have parameters:
<name> <mode> <type>
<mode> is one of {IN, OUT, INOUT}
eg: IN val1 int
CREATE PROCEDURE IncreaseRating( IN sailor_sid INTEGER, IN increase INTEGER)
UPDATE Sailors
SET rating = rating + increase WHERE sid = sailor_sid;

6. Stored Procedures: Examples
Stored procedure do not have to be in SQL:
CREATE PROCEDURE TopSailors( IN num INTEGER)
LANGUAGE JAVA
EXTERNAL NAME “file:///c:/storedProcs/rank.jar”

7. Example: Procedure in PSM
CREATE PROCEDURE testProcedure
BEGIN
INSERT INTO Student VALUES (5, ‘Joe’);
END;
Oracle’s version of PSM :
CREATE PROCEDURE testProcedure IS .
run;
NOTE: mySQL later versions have initial support.

8. Also You can drop procedure by DROP PROCEDURE <procedureName>
In PL/SQL, you can replace procedure by
CREATE OR REPLACE PROCEDURE <procedureName> …

9. Calling Stored Procedures
Calling Procedures
call <procedureName> [(<paramList>)];
Embedded SQL:
EXEC SQL BEGIN DECLARE SECTION
Int sid;
Int rating;
EXEC SQL END DECLARE SECTION
// now increase rating of this sailor
EXEC CALL IncreaseRating(:sid,:rating);

10. Stored Procedures : Persistent Stored Modules (PSM)

11. SQL/PSM
Most DBMSs allow users to write stored procedures in a simple general-purpose language (close to SQL)
SQL/PSM standard is a representative of vendor-specific languages.
Oracle supports a slightly different version of PSM called PL/SQL

12. Local Declarations
CREATE PROCEDURE testProcedure (num IN int, name IN varchar) IS
BEGIN
INSERT INTO Student VALUES (num, name);
END;

13. Local Declarations
CREATE PROCEDURE testProcedure (num IN int, name IN varchar) IS
num1 int; local variable
BEGIN
num1 := 10;
INSERT INTO Student VALUES (num1, name);
END;

14. Other PSM features Assignment statements: PL/SQL
<varName> := <expression>

15. Control Structures: IF THEN ELSE
IF <condition> THEN
<statementList>
ELSIF <condition> THEN
ELSIF …
ELSE <statementList>
END IF;

16. Loops LOOP <statementList> END LOOP; To exit from a loop use

17. Loops: Example
CREATE PROCEDURE testProcedure (num IN int, name IN varchar) IS
num1 int;
BEGIN
num1 := 10;
LOOP
INSERT INTO Student VALUES (num1, name);
num1 := num1 + 1;
IF (num1 > 15) THEN EXIT; END IF;
END LOOP;
END;

18. FOR Loops
FOR i in [REVERSE] <lowerBound> .. <upperBound> LOOP
<statementList>
END LOOP
Example:
FOR i in LOOP
INSERT INTO Student (sNumber) values (10 + i);
END LOOP;

19. WHILE LOOPS WHILE <condition> LOOP <statementList>
END LOOP;

20. Functions
CREATE FUNCTION <functionName> [(<paramList>)] RETURNS type AS
<localDeclarations>
BEGIN <functionBody>; END;
You can call a function as part of an SQL expression
Drop a function:
drop function <functionName>

21. Functions: Example CREATE FUNCTION testFunction RETURN int AS
num1 int;
BEGIN
SELECT MAX (sNumber) INTO num1 FROM Student;
RETURN num1;
END;
SELECT * from Student where sNumber = testFunction ();

22. SQL/PSM Example
CREATE FUNCTION rate Sailor (IN sailorId INTEGER) RETURNS INTEGER
DECLARE rating INTEGER;
DECLARE numRes INTEGER;
BEGIN
SET numRes = (SELECT COUNT(*)
FROM Reserves R WHERE R.sid = sailorId);
IF (numRes > 10) THEN rating =1;
ELSE rating = 0;
END IF;
RETURN rating;
END

23. Other Info Re Oracle :
Oracle stores procedures and functions in catalog as relational tables:
Check user_procedures
Check user_functions
You may run queries against them such as:
describe user_procedures;
select object_name from user_procedures;

24. Summary : Stored Procedures
Stored procedures execute application logic directly at the server
SQL/PSM standard for writing stored procedural logic:
Used stand-alone on explicit call
Used functions in WHERE clause of SQL statement
Used in body of triggers