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CommerceCommerceTutorial 6Tutorial 6

CGI/Perl and databases

DatabasesDatabases Defn: A database is a collection of data that is organized so that

its contents can easily be accessed, managed, and updated.[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

Databases ContinuedDatabases 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.

Figure 1: Showing table in database

  Figure2: Showing recordset returned for a query

Structured Query Language Structured Query Language (SQL)(SQL)

A programming language, that allows access to a database.

SQL Data Manipulation Language (DML) SQL Data Definition Language (DDL)

SQL Data Manipulation Language SQL Data Manipulation Language (DML)(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

SELECT SYNTAXSELECT 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

UPDATE SYNTAXUPDATE 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#

DELETE and INSERT DELETE and INSERT SYNTAXSYNTAX

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')

SQL Data Definition Language SQL Data Definition Language (DDL)(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

DDL SYNTAXDDL 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

Database connection stringsDatabase 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.

JDBC

[1] http://www.webopedia.com/TERM/O/ODBC.html

Connection String in PerlConnection String in Perl

$dbh=DBI->connect('dbi:Oracle' ,$username,$password);

DBI = Database Independent Module, allows for access to a supported SQL database

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

Useful LinksUseful Links

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