COMP 321 Week 4

Overview Normalization Entity-Relationship Diagrams SQL JDBC/JDBC Drivers hsqldb Lab 4-1 Introduction

Relational Databases Store data in tables made up of rows and columns Columns have data types Rows represent entries

Relational Databases Product_CodeDescriptionPrice Toaster Hair Dryer Car Vacuum CREATE TABLE Product ( Product_Code CHAR(11), Description CHAR(40), Price DECIMAL(10, 2) )

Normalization What’s wrong with this table definition? CREATE TABLE Order ( Product_Code CHAR(11), Quantity INTEGER, Description CHAR(40), Price DECIMAL(10, 2) )

Normalization What’s wrong with this table definition? CREATE TABLE Order ( Order_Id INTEGER, Product_Code CHAR(11), Quantity INTEGER, Description CHAR(40), Price DECIMAL(10, 2) )

Avoid Duplication – Create Two Tables CREATE TABLE Order ( Order_Id INTEGER PRIMARY KEY, Product_Code CHAR(11), Quantity INTEGER ) CREATE TABLE Product ( Product_Code CHAR(11) PRIMARY KEY, Description CHAR(40), Price DECIMAL(10, 2) )

Learning Activity 1 Problem description: –Normalize the following database definition. The intention is to represent an order with information about the customer, the order, and multiple line items.

Learning Activity 2 Problem description: –Draw an entity-relationship diagram for the tables you designed for storing orders.

SQL Four basic statements: oSELECT - selects data from tables oINSERT - inserts new data into a table oUPDATE - modifies existing rows in a table oDELETE - removes rows from a table

SQL (cont’d) SELECT * FROM Customer –Selects all columns from Customer table SELECT City, State FROM Customer –Selects only the City and State columns SELECT * FROM Customer WHERE State = ‘CA’ –Selects all customers who live in CA SELECT COUNT(*) FROM Customer WHERE State = ‘CA’ –Counts number of rows where State is CA

SQL (cont’d) INSERT INTO Customer VALUES (‘John Doe’, ‘Columbus’, ‘OH’) –Inserts a new customer record UPDATE Customer SET State = ‘OH’ WHERE State = ‘CA’ –Moves all customers who live in CA to OH DELETE FROM Customer –Deletes all rows from the Customer table DELETE FROM Customer WHERE State = ‘CA’ –Deletes all customers who live in CA

JDBC Java DataBase Connectivity - a set of classes and interfaces defined in the java.sql package Allows Java applications to connect to databases in a (mostly) database- independent way

JDBC (cont’d) The classes in java.sql are defined in a generic way, so they can be used with many databases The database-specific code is contained in a driver, which is usually provided by the database vendor Drivers are manipulated using the DriverManager class from java.sql

JDBC

JDBC Driver Types Type 1: JDBC-ODBC Bridge Type 2: Native API Driver Type 3: Network Protocol Driver Type 4: Native Protocol Driver

Type 1 - JDBC - ODBC Bridge Pros: Database independent Cons: –Windows only –Performance –ODBC driver must be present

Type 2 – Native API Driver Pros: better performance vs. type 1 Cons: –Client library must be present –Platform-dependant

Type 3 - Network Protocol Driver Pros: –No database library on client –Client is DB-independent Cons: –Extra layer –DB-specific coding required in middleware

Type 4 – Native Protocol Driver Pros: –Best performance –Pure Java Cons: –Driver required for each database

Using JDBC Identify type of driver needed Obtain/Install driver Add driver to classpath (In Eclipse, configure build path)

Making a Connection to the DB Manually load the driver class*: Class.forName("org.hsqldb.jdbcDriver"); Establish connection conn = DriverManager.getConnection( "jdbc:hsqldb:hsql://localhost:9001", "jdbc:hsqldb:hsql://localhost:9001", "sa", // username "sa", // username ""); // password ""); // password DriverManager takes care of details * Starting with JDBC4 (part of Java 6), the driver is loaded automatically

Statement Types Statement : SQL is sent to database each time PreparedStatement : compiled version of statement is cached and executed more than once CallableStatement : used to call stored procedures

JDBC Statements Statement stmt = conn.createStatement(); String cmd = "INSERT INTO Users ('User1', 'Password')"; try { stmt.executeUpdate(cmd); } finally { stmt.close(); }

ResultSet Connection conn = null; Statement stmt = conn.createStatement(); try { ResultSet rs = stmt.executeQuery("SELECT * FROM PRODUCT"); try { while (rs.next()) { int id = rs.getInt("ITEMID"); double price = rs.getDouble("PRICE"); String desc = rs.getString("DESCRIPTION"); // Do something with data } finally { rs.close(); } finally { stmt.close(); }

ResultSet Statement stmt = conn.createStatement(); try { ResultSet rs = stmt.executeQuery("SELECT ID,PRICE,DESC FROM PRODUCT"); try { while (rs.next()) { int id = rs.getInt(1); double price = rs.getDouble(2); String desc = rs.getString(3); // Do something with data } finally { rs.close(); } finally { stmt.close(); }

hsqldb % Java Database Open-source database we will be using for labs We will be using the latest version: RC 9

hsqldb - Installation Instructions Download and unzip into a local directory (for example C:\java\db\hsqldb) Create.cmd file to start hsqldb server C:\java\db\hsqldb\data\StartHSQLDB.cmd) cd C:\java\db\hsqldb\data java -cp../lib/hsqldb.jar org.hsqldb.server.Server --database.0 file:mydb --dbname.0 xdb

Validate Installation Start server, and run Testdb class from documentation Start with Testdb.java (in Week 4 folder on Website) Add hsqldb.jar to build path

hsqldb CREATE SCHEMA PUBLIC AUTHORIZATION DBA CREATE MEMORY TABLE SAMPLE_TABLE(ID INTEGER GENERATED BY DEFAULT AS IDENTITY(START WITH 0) NOT NULL PRIMARY KEY,STR_COL VARCHAR(256),NUM_COL INTEGER) ALTER TABLE SAMPLE_TABLE ALTER COLUMN ID RESTART WITH 8 CREATE USER SA PASSWORD "" GRANT DBA TO SA SET WRITE_DELAY 10 SET SCHEMA PUBLIC INSERT INTO SAMPLE_TABLE VALUES(0,'Ford',100) INSERT INTO SAMPLE_TABLE VALUES(1,'Toyota',200) INSERT INTO SAMPLE_TABLE VALUES(2,'Honda',300) INSERT INTO SAMPLE_TABLE VALUES(3,'GM',400) INSERT INTO SAMPLE_TABLE VALUES(4,'Ford',100) INSERT INTO SAMPLE_TABLE VALUES(5,'Toyota',200) INSERT INTO SAMPLE_TABLE VALUES(6,'Honda',300) INSERT INTO SAMPLE_TABLE VALUES(7,'GM',400)

Lab 4-1 Database (Hypersonic) Set Up Due May 30 th !