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Java and Databases

CS-328

Dick Steflik

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Database Drivers

Think of a database as just another device

connected to your computer

like other devices it has a driver program to

relieves you of having to do low level

programming to use the database

the driver provides you with a high level api

to the database

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ODBC

Open Data Base Connectivity

Developed by Microsoft for the Windows

platform as the way for Windows

applications to access Microsoft databases

(SQL Server, FoxPro, Access)

Has become an industry standard

Most data base vendors supply native, odbc,

and jdbc drivers for their data base products

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JDBC Driver Types

Type 1

JDBC-ODBC Bridge

Type 2

Native API, partially java

Type 3

JDBC Network Driver, partially java

Type 4

100% Java

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Type 1 Drivers

Translate JDBC into ODBC and use

Windows ODBC built in drivers

ODBC must be set up on every client

driver must be physically on each machine for

both java applications and applets

for server side servlets ODBC must be set upon web server

driver sun.jdbc.odbc.JdbcOdbc provided by

JavaSoft with JDK

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Type 1 Driver (cont.)

Client JDBC-

ODBC

ODBC DB

Vendor

Library

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Type 2 Drivers

Converts JDBC to data base vendors native

SQL calls

like Type 1 drivers; requires installation of

binaries on each client

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Type 2 Drivers (cont.)

Client JDBC

Vendor

Library

DB

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Type 3 Drivers

Translates JDBC to a DBMS independent

network protocol

Typically talks directly with a middleware

product which in turn talks to the RDBMS

Jaguar, DBAnywhere, SequeLink

Most flexible driver type

all java

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Type 3 Drivers (cont.)

Client JDBC Vendor

MiddlewareDB

Tier 1 Tier 2 Tier 3

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Type 4 Drivers

Converts JDBC directly to native API used

by the RDBMS

compiles into the application , applet or

servlet; doesnt require anything to be

installed on client machine, except JVM

handiest driver type

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Type 4 Drivers (cont.)

Client JDBC DB

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Structured Query Language

Developed by C. Date for Relational Data

Base Management Systems (RDBMS)

Simple Declarative Language

has no program control statements

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SQL

Two categories of commands

Data Manipulation Commands

deal with:

RETRIEVING DATA

MAINTAINING DATA (ADDING,

UPDATING,DELETING

Data Definition Commands DEAL WITH:

CREATING DATABASE OBJECTS (TABLES,VIEWS)

Object organization and attributes

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Referential Integrity

Rules to insure that table data stays accurate

and accessible

rows in a table should be unique

one column should contain no duplicate data

primary key

column values cannot contain repeating groupsor arrays

null is different than space and zero, 2 null

values are not considered equal

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Data Manipulation Commands

Select - query and display data from a

database

Insert - a new row into a table

Update - modify a column in a table

Delete a row from a table

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Select

Select (column list) from (sources) where (conditions) order by (ocolumn list)

column list - comma separated list of names of columns to be in output

Ex. ssn , lastname , firstname,gpa

can contain literals to be included in output Ex. Ssn,~,lastname,~,firstname

sources - name(s) of table(s) to retrieve data from

conditions (optional) - conditions for selections

lastname like S%

(lastname = Steflik) and (firstname like R%)

ocolumn list (optional)- list of columns that output should be ordered by

Ex

select * from student

select lastname,fristname from student where gpa > 3.0

select lastname,firstname from student order by lastname,firstname

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Select - joined tables

Two tables may be joined and viewed as a

single data source is the both have a

common column

suppose we have 2 tables: Inventory and

category and each has a column called

catg_code

In category catg_code is unique and is the

primary key

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Select - joined tables (cont.)

P_no Catg_code qty Catg_code descr

Inventory Category

join

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Select - joined tables (cont.)

To retrieve all of the part numbers and the

name of the category to which the part

belongs: select inventory.p_no category.descr from inventroy , category

select a.p_no, ,b.descr from a inventory , b category

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Insert

Add a row to a table insert into category values(IGN,Ignition System)

use jdbc execute Update method ex. Stmt.executeUpdate(insert into Category values(IGN,Ignition System));

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Update

Modify an existing row in a table update category set descr = Ignition Subsystem where catg_code = IGN

Use jdbc executeUpdate method String s = update category set descr = Ignition Subsystem where catg_code =

IGN ;

stmt.executeUpdate(s);

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Delete

Remove a row from a table delete from category where catg_code = IGN

remove the IGN category

delete from category where catg_code like I% remove all rows where catg_code starts with an I

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Data Definition Commands

Create table

add a table to a database

Drop Table

remove a table from a database

Alter Table

add or delete column(s)