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Database Programming:
Overview
1.
2.
Contents
The Impedance Mismatch
JDBC
1.
2.
3.
From the Elmasri/Navathe text
From the ASU scholars
PLSQL: by Prof. James Dullea, VU
Slide 1 of 36
The Impedance Mismatch


It’s the disconnect between the
approach of a database language and
that of a conventional programming
language in which it’s embedded: the
former uses tables (sets of rows), while
the latter uses a record at a time.
Note how each of JDBC and PL/SQL
addresses this.
Slide 2 of 36
Next up: JDBC


From the Elmasri/Navathe text
From the ASU scholars
Slide 3 of 36
Chapter 9
Introduction to SQL
Programming Techniques
Copyright © 2007 Ramez Elmasri and Shamkant B.
Navathe
Java Database Connectivity

JDBC:



SQL connection function calls for Java
programming
A Java program with JDBC functions
can access any relational DBMS that
has a JDBC driver
JDBC allows a program to connect to
several databases (known as data
sources)
Slide 9- 5
Steps in JDBC Database Access
1.
2.
3.
4.
5.
6.
7.
8.
9.
Import JDBC library (java.sql.*)
Load JDBC driver:
Class.forname(“oracle.jdbc.driver.OracleDrive
r”)
Define appropriate variables
Create a connect object (via getConnection)
Create a statement object from the Statement class:
 1. PreparedStatment 2. CallableStatement
Identify statement parameters (designated by question
marks)
Bound parameters to program variables
Execute SQL statement (referenced by an object) via
JDBC’s executeQuery
Process query results (returned in an object of type
ResultSet)
 ResultSet is a 2-dimentional table
Slide 9- 6
Embedded SQL in Java:
An Example
ssn = readEntry("Enter a SSN: ");
try {
#sql{select FNAME< LNAME, ADDRESS, SALARY
into :fname, :lname, :address, :salary
from EMPLOYEE where SSN = :ssn};
}
catch (SQLException se) {
System.out.println("SSN does not exist:
",+ssn);
return;
}
System.out.println(fname + " " + lname + … );
Slide 9- 7
ADVANCED DATABASE CONCEPTS
JDBC
Susan D. Urban and Suzanne W. Dietrich
Department of Computer Science and Engineering
Arizona State University
Tempe, AZ 85287-5406
WEB/DB
8
OPEN DATABASE
CONNECTIVITY (ODBC)




WEB/DB
Standard application programming interface
(API) for accessing a database.
A separate module or driver is required for
each database to be accessed.
Based on the standard Call Level Interface
(CLI) of the SQL Access Group (part of the
X/Open Standard).
Can use the API to execute SQL statements,
update tables, and retrieve metadata.
9
ODBC ISSUES IN A JAVA
ENVIRONMENT



WEB/DB
ODBC uses C to access the data source. This
poses issues with implementation. Hence, it
cannot be used in conjunction with Java.
OBDC’S API cannot be used by translating the
API to Java since there is no pointer concept
in Java.
ODBC requires the driver manager to be
installed on every client installation.
10
JAVA DATABASE
CONNECTIVITY (JDBC)






WEB/DB
Java API for connecting programs written in
Java to databases.
Based on ODBC.
Allows Java programs to send SQL
statements to any relational database.
Platform independent.
JDBC drivers written in Java can be accessed
from any computer in a heterogeneous
network .
A JDBC-ODBC bridge can be used to access
databases using the ODBC interface.
11
TWO-TIER JDBC
ARCHITECTURES



Java application or applet talks directly to the
data source.
Client sends requests to the server through user
interfaces.
JDBC Driver communicates with the data source
to access the data.
Sun Microsystems Inc. 1999
WEB/DB
12
THREE-TIER JDBC
ARCHITECTURES



Uses a third tier between the client and the
server.
Controls updates that are made to the database.
Secure and robust.
Sun Microsystems Inc. 1999
WEB/DB
13
DEVELOPING JDBC
APPLICATIONS





Import JDBC classes (java.sql.*)
Load the JDBC Driver.
Connect to the database.
Use the JDBC API to access the database.
Disconnect from the database.
WEB/DB
14
CONNECTION
TO A DATABASE





The first step in accessing data from any
relational database using JDBC is to establish a
connection with the data source.
The Connection object is used to get meta data
and execute SQL statements.
The getConnection method returns a Connection
object that represents a session with a specific
database.
The parameters in the getConnection method are
URL, username and password. Username and
password are optional.
The URL consists of the protocol “jdbc”, subprotocol “odbc”, and the Data Source Name
(DSN).
WEB/DB
15
EXAMPLE TO CONNECT TO A
DATABASE
/* dbName is the registered name of the ODBC data source */
String url = "jdbc:odbc:" + dbName ;
try {
/* Load the jdbc-odbc driver */
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
/* Open a connection to the odbc data source */
con =DriverManager.getConnection(url,"","");
}
WEB/DB
16
STATEMENTS


WEB/DB
A Statement Object is used to send SQL
queries to a database.
A Statement object should be created using
the connection method createStatement().
17
TYPES OF STATEMENTS
There are three types of statement objects:
 Simple statements
Used to execute SQL statements without any
parameters.
Statement stmt = connection.createStatement();

Prepared Statements
Used when a statement will be called several times and
is stored as a pre-compiled statement with IN
parameters.
PreparedStatement pstmt =
con.prepareStatement(“update employee set salary=? where ssn=?”);

WEB/DB
Callable Statements
Used with calls to database stored procedures and
SQL statements with OUT parameters.
18
EXECUTING SIMPLE
STATEMENTS

The execution of a statement returns results into
a ResultSet object. The ResultSet object is then
used to access query results.
ResultSet rs = null;

The executeQuery() method is used to execute
an SQL statement through the statement object.
rs = stmt.executeQuery("SELECT a, b, c FROM Table1");

The close() method is used to close the
ResultSet.
rs.close();
WEB/DB
19
GETTING DATA FROM A
ResultSet



The next() method is used to traverse
through tuples in the ResultSet object.
The data stored in a ResultSet object is
retrieved through a set of get methods that
allows access to the various columns of the
current row.
The results are printed out on a screen using
the Servlet output stream.
while(rs.next())
{
out.println(rs.getString(“SSN”));
}
WEB/DB
20
DATABASE METADATA

Metadata is the information in the database
that is associated with the database schema:





WEB/DB
Table names
Column names
Column types
The metadata associated with a database can
be queried using JDBC.
The metadata associated with the result set
object of a statement execution can also be
queried.
21
DATABASE METADATA
RETRIEVAL

Create a metadata object.
DatabaseMetaData dbmd ;

Retrieve metadata from the database through
the connection established.
dbmd = con.getMetaData();

The getTables() method of the metadata
object is used to retrieve information about
the tables in a database. The information is
stored in a result set object.
ResultSet rsTables = dbmd.getTables(null, null, null, null);
WEB/DB
22
GETTING THE METADATA

The getString() method of the ResultSet
object is used to locate a specific table.
String tableName = rsTables.getString("TABLE_NAME");

The getColumns() method is used to retrieve
information about the columns and column
types in a table, with the results stored in a
ResultSet object.
ResultSet rsColumns =
dbmd.getColumns(null,null,tableName,null);
while (rsColumns.next())
{
…
}
WEB/DB
23
Next up: PL/SQL
By Prof. James Dullea
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 24 of 36
7 From Prof. Dullea
CSC8490
Introduction to PL/SQL
Dr. James Dullea
[email protected]
Module 01-9
Revised: June 12, 2005
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 25 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)
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 26 of 36
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
Slide 27 of 36
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 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.
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 28 of 36
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 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.
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 29 of 36
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
Slide 30 of 36
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
Slide 31 of 36
PL/SQL Build-In Utility Packages
DBMS_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
Slide 32 of 36
PL/SQL Build-In Utility Packages
Example
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
Slide 33 of 36
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
Slide 34 of 36
Data Types
Scalar 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
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 35 of 36
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
Slide 36 of 36
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
Slide 37 of 36
Conditional Statements
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;
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 38 of 36
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
Slide 39 of 36
Loop Structures




Unconstrained loops
WHILE loop
FOR loop
GOTO <<LABEL>>
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 40 of 36
Unconstrained Loops
LOOP
<sequence of statements>
EXIT WHEN <condition>
<sequence of statements>
END LOOP;
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 41 of 36
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
Slide 42 of 36
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
Slide 43 of 36
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
Slide 44 of 36
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
Slide 45 of 36
Block Structure for PL/SQL Subprograms
(Procedures or Functions)






Program Comments
Header
IS|AS
Declaration Section
BEGIN
Executable Section
EXCEPTION
Exception Section
END;
/
(optional)
(mandatory)
(mandatory)
(mandatory)
(optional)
(mandatory)
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 46 of 36
Block Structure for PL/SQL subprograms
Completed 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
Slide 47 of 36
Execution of a Stored
Functions
EXEC
AddDepartment ('Info Center', 43, '888665555', '28JUN-2005');
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 48 of 36
Syntax of a Stored Functions
CREATE OR REPLACE FUNCTION function_name
(parameters IN datatypes)
RETURN datatype
IS|AS
Declaration Section
BEGIN
Executable Section
RETURN variable_name
EXCEPTION (optional)
Exception Section
END;
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 49 of 36
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
Slide 50 of 36
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
Slide 51 of 36
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
Slide 52 of 36
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
Slide 53 of 36
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
Slide 54 of 36
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
Slide 55 of 36
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
Slide 56 of 36
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
Slide 57 of 36
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
Slide 58 of 36
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
MINIT
LNAME
SSN
BDATE
STREET
CITY
STATE
ZIP
SEX
SALARY
SUPERSSN
DNO
use your first name
use your middle init or a blank space
use your last name
make up a 9 digit number
use your birthday (be careful of the date format)
make up data
Villanova
PA
use the Villanova zip code
M or F
38000
333445555
5
Dr. James Dullea, CSC8490
Introduction to PL/SQL
Slide 59 of 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
Slide 60 of 36