CIS 270—App Dev II Big Java Chapter 22 Relational Databases

Database Tables A relational database (DB) stores information in _________. Tables contain data in rows and __________. Columns represent data ________ such as SSN, Name, DateOfBirth, etc. Rows represent individual _________ such as students (which have SSN, Name, DateOfBirth, …). Data in relational databases are accessed using SQL (structured query ___________). Java can be used to send SQL commands to a DB. tables columns fields entities language

SQL Examples SQL command to create a product table: CREATE TABLE Product ( Product_Code CHAR(11), Description CHAR(40), Price DECIMAL(10, 2) ) Insert a _____ in a table: INSERT INTO Product VALUES (‘ ’, ‘Hair dryer’, 29.95) Remove a table from the DB: DROP TABLE Product row

Linking Tables A Customer class can have _________ fields that directly relate to columns in a relational table. – Customer table: customerId, name, address, city, state, zip However, an Invoice class may have a Customer object as an instance field (more complicated). This situation would require an Invoice table: – Invoice table: invoiceId, customerId, payment These two tables are linked by the customerId field, which is the primary _____ of Customer and a __________ key of Invoice. instance key foreign

Implementing Relationships Each invoice has exactly one customer, which is a _____ relationship (single-valued). But an invoice can have many line items (____ or multi-valued relationship): – private ArrayList items; This requires two more tables. – LineItem table: invoiceId, productId, quantity – Product table: productId, description, price Tables and relationships: Customer --- Invoice --- LineItem --- Product 1:1 1:n 1:1 1:n1:1

22.2 Queries I Use the SELECT command to _______ a database: – SELECT city, state FROM Customer – SELECT * FROM Customer WHERE State = ‘CA’ – SELECT * FROM Customer WHERE Name LIKE ‘_o%’ – SELECT * FROM Product WHERE Price < 100 AND Description <> ‘Toaster’ Above, the _ means ‘match ____ character’ and the % means ‘match any number of characters’ Calculations: – SELECT AVG(Price) FROM Product query one

22.2 Queries II Joins – SELECT LineItem.invoice_number FROM Product, LineItem WHERE Product.description = ‘Car vacuum’ AND Product.product_code = LineItem.product_code Updating and Deleting Data – DELETE FROM Customer WHERE State = ‘CA’ – UPDATE LineItem SET quantity = quantity + 1 WHERE invoice_number = ‘11731’

22.4 Create a DB and a DSN Create a database using Access and save to a folder Create a DSN (data ________ name) for the database – In Windows, click Start, Settings, Control Panel – Double-click Administrative Tools – Double-click Data Sources (ODBC) – Click User DSN tab – Click Add button – Select Microsoft Access Driver (*.mdb, *.accdb), click Finish – Enter a Data Source Name (your choice) – Click the Select button, navigate to the folder containing the database, select the database, click the database file – Click OK, OK, and OK source

22.4 Write the Java Program I Create a Connection object import java.sql.Connection; import java.sql.Statement; import java.sql.DriverManager; import java.sql.ResultSet; public class Test { public static void main( String[] args ) { try { Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" ); String dataSourceName = "mdbTEST"; String dbURL = "jdbc:odbc:" + dataSourceName; Connection con = DriverManager.getConnection( dbURL, "","" );

22.4 Write the Java Program II Create an SQL Statement object and use it to execute various SQL commands Statement stmt = con.createStatement(); stmt.execute( “CREATE TABLE Table1 ( aColumnName integer )” ); stmt.execute( “INSERT INTO Table1 VALUES( 77 )” ); stmt.execute( “SELECT aColumnName FROM Table1” );

22.4 Write the Java Program III Create a ResultSet object and use it to display results ResultSet rs = stmt.getResultSet(); if ( rs != null ) while ( rs.next() ) { System.out.println( "Data from first column: " + rs.getString( 1 ) ); } stmt.execute( “DROP TABLE Table1" ); stmt.close(); con.close(); } // end try

22.4 Write the Java Program IV Finish up catch ( Exception err ) { System.out.println( "ERROR: " + err ); } // end catch } // end main } // end class Install the database, compile the Java program and run See code.com/vb/scripts/ShowCode.asp?txtCodeId=2 691&lngWId=2#SECTION_SQL for more discussionhttp:// code.com/vb/scripts/ShowCode.asp?txtCodeId=2 691&lngWId=2#SECTION_SQL