1. ECMM6018 Enterprise Networking For Electronic Commerce Tutorial 6 CGI/Perl and databases

2. Databases Defn: A database is a collection of data that is organized so that its contents can easily be accessed, managed, and updated.[1][1] Different types of databases i. Relational Database: Stores data in the form of related tables ii.Object Oriented Programming Database: This has the data defined in objects classes and sub classes. Some of the Databases in use: IBM's DB2, Microsoft's Access, MySQL, Postgresql and products from Oracle, Sybase, and Computer Associates. [1] http://searchdatabase.techtarget.com/sDefinition/0,,sid13_gci211895,00.html [1]

3. Databases Continued For DBMS a record is collection of fields each field containing one entry In databases records are also known as tuples Recordset – collection of records returned which match the query entered.

4. Figure 1: Showing table in database

5. Figure2: Showing recordset returned for a query

6. Structured Query Language (SQL) A programming language, that allows access to a database. SQL Data Manipulation Language (DML) SQL Data Definition Language (DDL)

7. SQL Data Manipulation Language (DML) This allows us to either extract, insert, delete or update data in the database SELECT - extracts data from a database table UPDATE - updates data in a database table DELETE - deletes data from a database table INSERT INTO - inserts new data into a database table

8. SELECT SYNTAX SELECT column_name(s) FROM table_name WHERE clause: This allows us to conditionally select data from a table based upon some criteria SELECT column FROM table WHERE column operator value e.g. Select * from nur

9. UPDATE SYNTAX UPDATE table_name SET column_name = new_value WHERE column_name = some_value e.g. update #period# set period ='#period#', Primary='#form.Primary#',Last1='#form.Last1#', First1'#form.First1#',Last2='#form.Last2#',First2='#form.First2#',editor_last1='#editor_last1# where key=#form.key#

10. DELETE and INSERT SYNTAX DELETE FROM table_name WHERE column_name = some_value e.g. delete from nur where l_name='zincir' INSERT INTO table_name VALUES (value1, value2,....) e.g. insert into nur (l_name,f_name) values ('lastname1','firstname1')

11. SQL Data Definition Language (DDL) This allows us to create or delete tables in the database. CREATE TABLE - creates a new database table ALTER TABLE - alters (changes) a database table DROP TABLE - deletes a database table

12. DDL SYNTAX CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type,....... ) ALTER TABLE table_name ADD column_name datatype ALTER TABLE table_name DROP COLUMN column_name

13. Database connection strings ODBC (Object Database Connectivity) – An application interface for accessing a database. Makes it possible to assess data from any application irrelevant of the underlying DBMS used. It carries out this task by inserting a middle layer known as a driver between the application and the DBMS. The role of this is to convert application's data queries into commands that the DBMS understands.[1] It is also language independent.[1] JDBC [1][1] http://www.webopedia.com/TERM/O/ODBC.html

14. Connection String in Perl $dbh=DBI->connect( 'dbi:Oracle',$username,$password); DBI = Database Independent Module, allows for access to a supported SQL database

15. Using a database through the DBI module Connect to the database Prepare the SQL statement and return a statement handle Using the Statement handle, Execute the SQL statement If the SQL statement is a SELECT, use the Statement handle to get the SELECTed records Close the statement handle Close the connection

16. Useful Links http://www.suite101.com/article.cfm/perl/67813 http://www.saturn5.com/~jwb/dbi-examples.html