Java and Databases
CS-328
Dick Steflik
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
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
JDBC Architecture
Java Application
JDBC API
Data Base Drivers
Access
SQL
Server
DB2
Informix
MySQL
Sybase
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
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 up
on web server
• driver sun.jdbc.odbc.JdbcOdbc provided by
JavaSoft with JDK
Type 1 Driver (cont.)
Client
JDBCODBC
Vendor
Library
ODBC
DB
Type 2 Drivers
• Converts JDBC to data base vendors native
SQL calls
• like Type 1 drivers; requires installation of
binaries on each client
Type 2 Drivers (cont.)
Client
JDBC
Vendor
Library
DB
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
Type 3 Drivers (cont.)
Client
JDBC
Tier 1
Vendor
Middleware
Tier 2
DB
Tier 3
Type 4 Drivers
• Converts JDBC directly to native API used
by the RDBMS
• compiles into the application , applet or
servlet; doesn’t require anything to be
installed on client machine, except JVM
• handiest driver type
Type 4 Drivers (cont.)
Client
JDBC
DB
Structured Query Language
• Developed by C. Date for Relational Data
Base Management Systems (RDBMS)
• Simple Declarative Language
– has no program control statements
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
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 groups
or arrays
– null is different than space and zero, 2 null
values are not considered equal
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
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
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
Select - joined tables (cont.)
join
Inventory
P_no
Catg_code
qty
Category
Catg_code
descr
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
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’)”);
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);
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”
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)