**Perl** is a dynamic programming language. It is often used to code the back-end for applications that use a database to store information.

To connect to a database, Perl uses the **DBI** (Database Independent Interface) module. The DBI module provides a layer of abstraction between our Perl code and the database.

To communicate with the database, DBI uses **Structured Query Language** otherwise knows as SQL.

# Connecting

To connect to a database, the `connect()` method is invoked.

The function takes the following input parameters:

1. **Data source name:** This is a string that contains the name of our module, the database engine, and the name of the database that we wish to connect to.

2. **Username:** This string represents the username specific to the database we are trying to connect to

3. **Password:** The password for the database.

```perl
my $db_engine = "mysql"; 
my $database = "SAMPLEDB";
my $dsn = "DBI:$db_engine:$database";
my $user = "sampleuser";
my $pass = "sample123";

my $dbcon = DBI->connect($dsn, $user, $pass) or die $DBI::errstr();
```

If the connection is successful, a *Database Handle* is returned. In case of an error `$dbcon` is set to `undef` and `$DBI::errstr` returns an error string.

# Using queries

To prepare queries, the `prepare()` method is invoked. This is invoked via the connection variable.

An SQL query embedded within a string is passed as the input parameter to the `prepare()` method.

```perl
my $query = $dbcon->prepare("CREATE TABLE Employees(id INT PRIMARY KEY, name VARCHAR(10))");

$query->execute()
```

The above query is used to create a table in our database.

The `execute()` method executes the query in our database. The result table returned (if any) is then associated with our query variable.

The following functions can be used to access the row data of the result table returned.

- `fetchrow():` returns the next row of the table or `undef` in case of error.

- `fetchrow_array():` returns an array that contains the row data of the current row.

>We can disconnect from the database using the `disconnect()` method of the query variable.


# Code 
The following code shows how a database is connected to and accessed in Perl.

# import the DBI module
use DBI;

# connecting
my $db_engine = "mysql"; 
my $database = "SAMPLEDB";
my $dsn = "DBI:$db_engine:database=$database";
my $userid = "sampleuser";
my $password = "sample123";

my $dbcon = DBI->connect($dsn, $userid, $password ) or die $DBI::errstr();

# using queries

#--Creating table
my $query_ = $dbcon->prepare("CREATE TABLE Employees(id INT PRIMARY KEY, name VARCHAR(10)");
$query->execute()
#--Inserting values
my $query = $dbcon->prepare("INSERT INTO Employees VALUES(?, ?)");
my $id = 1;
my $name = "Alice";  
$query->execute($id, $name);
$query->execute($id + 1, "Bob");
#--Selecting all rows in Employees table
my $resultTable = $dbcon->prepare("SELECT * FROM Employees");
$resultTable->execute();
#--printing result
while (my @row = $resultTable->fetchrow_array()) 
{
    print "@row\n";
}
  
warn "Error", $resultTable->errstr( ), "\n"
if $resultTable->err();

# disconneting
$dbcon->disconnect()
  
exit;

>Note: The above code assumes that a database by the name `SAMPLEDB` has been created on the database server.

# Connecting

To connect to a database, the `connect()` method is invoked.

The function takes the following input parameters:

1. **Data source name:** This is a string that contains the name of our module, the database engine, and the name of the database that we wish to connect to.

2. **Username:** This string represents the username specific to the database we are trying to connect to

3. **Password:** The password for the database.

```perl
my $db_engine = "mysql"; 
my $database = "SAMPLEDB";
my $dsn = "DBI:$db_engine:$database";
my $user = "sampleuser";
my $pass = "sample123";

my $dbcon = DBI->connect($dsn, $user, $pass) or die $DBI::errstr();
```

If the connection is successful, a *Database Handle* is returned. In case of an error `＄dbcon` is set to `undef` and `＄DBI::errstr` returns an error string.

# Using queries

To prepare queries, the `prepare()` method is invoked. This is invoked via the connection variable.

An SQL query embedded within a string is passed as the input parameter to the `prepare()` method.

```perl
my $query = $dbcon->prepare("CREATE TABLE Employees(id INT PRIMARY KEY, name VARCHAR(10))");

$query->execute()
```

The above query is used to create a table in our database.

The `execute()` method executes the query in our database. The result table returned (if any) is then associated with our query variable.

The following functions can be used to access the row data of the result table returned.

- `fetchrow():` returns the next row of the table or `undef` in case of error.

- `fetchrow_array():` returns an array that contains the row data of the current row.

>We can disconnect from the database using the `disconnect()` method of the query variable.


# Code 
The following code shows how a database is connected to and accessed in Perl.

How to access a database using Perl

Perl, via the DBI module, connects to databases using SQL. Key methods include connect(), prepare(), and execute(). Functions fetchrow() and fetchrow_array() handle query results.