Java and Databases

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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 Architecture
Java Application
JDBC API
Data Base Drivers
Access
SQL Server
DB2
Informix
MySQL
Sybase
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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 up on
  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.)
JDBC
Client
DB
Vendor Library
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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.)
Vendor Middleware
Client
JDBC
DB
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 groups or
  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.)
join
Inventory
Category
P_no
Catg_code
qty
Catg_code
descr
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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)