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

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] [1]

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.

Figure 1: Showing table in database

Figure2: Showing recordset returned for a query

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

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

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

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#

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')

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

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

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]

Connection 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

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