Found 157 Articles for PERL

Perl UPDATE Operation on any database means to update one or more records already available in the database tables. Following is the procedure to update all the records having SEX as 'M'. Here we will increase AGE of all the males by one year. This will take three steps −Preparing SQL query based on required conditions. This will be done using prepare() API.Executing SQL query to select all the results from the database. This will be done using execute() API.Releasing Statement handle. This will be done using finish() API.If everything goes fine then commit this operation otherwise you can rollback complete transaction. See next ... Read More

Perl READ Operation on any databasse means to fetch some useful information from the database, i.e., one or more records from one or more tables. So once our database connection is established, we are ready to make a query into this database. Following is the procedure to query all the records having AGE greater than 20. This will take four steps −Preparing SQL SELECT query based on required conditions. This will be done using prepare() API.Executing SQL query to select all the results from the database. This will be done using execute() API.Fetching all the results one by one and ... Read More

Perl INSERT operation is required when you want to create some records into a table. Here we are using table TEST_TABLE to create our records. So once our database connection is established, we are ready to create records into TEST_TABLE. Following is the procedure to create single record into TEST_TABLE. You can create as many as records you like using the same concept.Record creation takes the following steps −Preparing SQL statement with INSERT statement. This will be done using prepare() API.Executing SQL query to select all the results from the database. This will be done using execute() API.Releasing Stattement handle. ... Read More

Assuming we are going to work with MySQL database with Perl. Before connecting to a database make sure of the followings. You can take help of our MySQL tutorial in case you are not aware about how to create database and tables in MySQL database.You have created a database with a name TESTDB.You have created a table with a name TEST_TABLE in TESTDB.This table is having fields FIRST_NAME, LAST_NAME, AGE, SEX and INCOME.User ID "testuser" and password "test123" are set to access TESTDB.Perl Module DBI is installed properly on your machine.You have gone through MySQL tutorial to understand MySQL Basics.Following ... Read More

If you have programmed using object oriented programming before, then you will be aware of the need to create a destructor to free the memory allocated to the object when you have finished using it. Perl does this automatically for you as soon as the object goes out of scope.In case you want to implement your destructor, which should take care of closing files or doing some extra processing then you need to define a special method called DESTROY. This method will be called on the object just before Perl frees the memory allocated to it. In all other respects, the ... Read More

Perl offers a feature which you would not find in any other programming languages: a default subroutine. Which means, if you define a function called AUTOLOAD(),  then any calls to undefined subroutines will call AUTOLOAD() function automatically. The name of the missing subroutine is accessible within this subroutine as $AUTOLOAD.Default autoloading functionality is very useful for error handling. Here is an example to implement AUTOLOAD, you can implement this function in your own way.sub AUTOLOAD {    my $self = shift;    my $type = ref ($self) || croak "$self is not an object";    my $field = $AUTOLOAD;    $field ... Read More

You can add your additional functions in child class or you can add or modify the functionality of an existing methods in its parent class. It can be done as follows −#!/usr/bin/perl package Employee; use Person; use strict; our @ISA = qw(Person);    # inherits from Person # Override constructor sub new {    my ($class) = @_;    # Call the constructor of the parent class, Person.    my $self = $class->SUPER::new( $_[1], $_[2], $_[3] );    # Add few more attributes    $self->{_id} = undef;    $self->{_title} = undef;    bless $self, $class;    return $self; } # ... Read More

Object-oriented programming has very good and useful concept called inheritance. Inheritance simply means that properties and methods of a parent class will be available to the child classes. So you don't have to write the same code again and again, you can just inherit a parent class.For example, we can have a class Employee, which inherits from Person. This is referred to as an "isa" relationship because an employee is a person. Perl has a special variable, @ISA, to help with this. @ISA governs (method) inheritance.Following are the important points to be considered while using inheritance −Perl searches the class ... Read More

Other object-oriented languages have the concept of security of data to prevent a programmer from changing an object data directly and they provide accessor methods to modify object data. Perl does not have private variables but we can still use the concept of helper methods to manipulate object data.Lets define a helper method to get person’s first name −sub getFirstName {    return $self->{_firstName}; }Another helper function to set person’s first name −sub setFirstName {    my ( $self, $firstName ) = @_;    $self->{_firstName} = $firstName if defined($firstName);    return $self->{_firstName}; }Now lets have a look into complete example: ... Read More

To create an instance of a class (an object) we need an object constructor in Perl. This constructor in Perl is a method defined within the package. Most programmers choose to name this object constructor method new, but in Perl you can use any name.You can use any kind of Perl variable as an object in Perl. Most Perl programmers choose either references to arrays or hashes.Let's create our constructor for our Person class using a Perl hash reference. When creating an object, you need to supply a constructor, which is a subroutine within a package that returns an object ... Read More