SQLite - `Perl`

Installation

SQLite3 can be integrated with Perl using the Perl DBI module. The Perl DBI module is the database access module for the Perl programming language. It defines a set of methods, variables, and conventions that provide a standard database interface.

The following shows the simple steps to install the DBI module on a Linux/UNIX machine:

$ wget http://search.cpan.org/CPAN/authors/id/T/TI/TIMB/DBI-1.625.tar.gz
$ tar xvfz DBI-1.625.tar.gz
$ cd DBI-1.625
$ perl Makefile.PL
$ make
$ make install

If you need to install the SQLite driver for DBI, you can follow these steps:

$ wget http://search.cpan.org/CPAN/authors/id/M/MS/MSERGEANT/DBD-SQLite-1.11.tar.gz
$ tar xvfz DBD-SQLite-1.11.tar.gz
$ cd DBD-SQLite-1.11
$ perl Makefile.PL
$ make
$ make install

DBI Interface API

The following are important DBI routines that satisfy the needs of using SQLite database in your Perl programs. For more details, please refer to the official Perl DBI documentation.

Number	API & Description
1	DBI->connect($data_source, "", "", \%attr) <br> Establishes a database connection or session to the requested $data_source. Returns a database handle object if the connection is successful. The data source format is as follows: DBI:SQLite:dbname='test.db'. Here, SQLite is the SQLite driver name, and test.db is the name of the SQLite database file. If the filename is assigned as ':memory:', it will create an in-memory database that persists only for the duration of the session. If the filename is an actual device file name, it will attempt to open the database file with that name. If the file does not exist, it will create a new database file with that name. You can leave the second and third parameters blank, and the last parameter is used to pass various attributes, as explained in the examples below.
2	$dbh->do($sql) <br> This routine prepares and executes a simple SQL statement. Returns the number of rows affected, or undef if an error occurs. A return value of -1 means the number of rows is unknown, not applicable, or unavailable. Here, $dbh is the handle returned by the DBI->connect() call.
3	$dbh->prepare($sql) <br> This routine prepares a statement for subsequent execution by the database engine and returns a statement handle object.
4	$sth->execute() <br> This routine performs any processing required to execute the prepared statement. Returns undef if an error occurs. It always returns true if the execution is successful, regardless of the number of rows affected. Here, $sth is the statement handle returned by the $dbh->prepare($sql) call.
5	$sth->fetchrow_array() <br> This routine fetches the next row of data and returns it as a list containing the field values. Null fields are returned as undef values in the list.
6	$DBI::err <br> This is equivalent to $h->err. Here, $h is any handle type, such as $dbh, $sth, or $drh. This routine returns the database engine error code for the last driver method called.
7	$DBI::errstr <br> This is equivalent to $h->errstr. Here, $h is any handle type, such as $dbh, $sth, or $drh. This routine returns the database engine error message for the last DBI method called.
8	$dbh->disconnect() <br> This routine closes the database connection previously opened by the DBI->connect() call.

Connecting to the Database

The following Perl code shows how to connect to an existing database. If the database does not exist, it will be created, and finally, a database object will be returned.

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite"; 
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";

my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 }) 
                      or die $DBI::errstr;

print "Opened database successfully\n";

Now, let's run the above program to create our database test.db in the current directory. You can change the path as needed. Save the above code in a file named sqlite.pl and execute it as shown below. If the database is created successfully, it will display the message shown below:

$ chmod +x sqlite.pl
$ ./sqlite.pl
Opened database successfully

Creating a Table

The following Perl code snippet will be used to create a table in the previously created database:

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(CREATE TABLE COMPANY
      (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL););
my $rv = $dbh->do($stmt);
if($rv < 0){
   print $DBI::errstr;
} else {
   print "Table created successfully\n";
}
$dbh->disconnect();

When the above program is executed, it will create the COMPANY table in test.db and display the message shown below:

Opened database successfully
Table created successfully

Note: If you encounter the following error in any operation:

DBD::SQLite::st execute failed: not an error(21) at dbdimp.c line 398

In this case, you will need to open the dbdimp.c file available in the DBD-SQLite installation, find the sqlite3_prepare() function, and change its third argument to -1 instead of 0. Finally, install DBD::SQLite using make and make install to resolve the problem.

INSERT Operation

The following Perl program shows how to create records in the COMPANY table created above:

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })

or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (1, 'Paul', 32, 'California', 20000.00 ));
my $rv = $dbh->do($stmt) or die $DBI::errstr;

$stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (2, 'Allen', 25, 'Texas', 15000.00 ));
$rv = $dbh->do($stmt) or die $DBI::errstr;

$stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (3, 'Teddy', 23, 'Norway', 20000.00 ));
$rv = $dbh->do($stmt) or die $DBI::errstr;

$stmt = qq(INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)
      VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 ););
$rv = $dbh->do($stmt) or die $DBI::errstr;

print "Records created successfully\n";
$dbh->disconnect();

When the above program is executed, it will create the given records in the COMPANY table and display the following two lines:

Opened database successfully
Records created successfully

SELECT Operation

The following Perl program shows how to fetch and display records from the COMPANY table created earlier:

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(SELECT id, name, address, salary  from COMPANY;);
my $sth = $dbh->prepare( $stmt );
my $rv = $sth->execute() or die $DBI::errstr;
if($rv < 0){
   print $DBI::errstr;
}
while(my @row = $sth->fetchrow_array()) {
      print "ID = ". $row[0] . "\n";
      print "NAME = ". $row[1] ."\n";
      print "ADDRESS = ". $row[2] ."\n";
      print "SALARY =  ". $row[3] ."\n\n";
}
print "Operation done successfully\n";
$dbh->disconnect();

When the above program is executed, it will produce the following result:

Opened database successfully
ID = 1
NAME = Paul
ADDRESS = California
SALARY =  20000

ID = 2
NAME = Allen
ADDRESS = Texas
SALARY =  15000

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY =  20000

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY =  65000

Operation done successfully

UPDATE Operation

The following Perl code demonstrates how to use the UPDATE statement to update any record, and then fetch and display the updated records from the COMPANY table:

```perl
#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(UPDATE COMPANY set SALARY = 25000.00 where ID=1;);
my $rv = $dbh->do($stmt) or die $DBI::errstr;
if( $rv < 0 ){
   print $DBI::errstr;
}else{
   print "Total number of rows updated : $rv\n";
}
$stmt = qq(SELECT id, name, address, salary  from COMPANY;);
my $sth = $dbh->prepare( $stmt );
$rv = $sth->execute() or die $DBI::errstr;
if($rv < 0){
   print $DBI::errstr;
}
while(my @row = $sth->fetchrow_array()) {
      print "ID = ". $row[0] . "\n";
      print "NAME = ". $row[1] ."\n";
      print "ADDRESS = ". $row[2] ."\n";
      print "SALARY =  ". $row[3] ."\n\n";
}
print "Operation done successfully\n";
$dbh->disconnect();

When the above program is executed, it produces the following result:

Opened database successfully
Total number of rows updated : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY =  25000

ID = 2
NAME = Allen
ADDRESS = Texas
SALARY =  15000

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY =  20000

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY =  65000

Operation done successfully

DELETE Operation

The following Perl code demonstrates how to use the DELETE statement to delete any record, and then fetch and display the remaining records from the COMPANY table:

#!/usr/bin/perl

use DBI;
use strict;

my $driver   = "SQLite";
my $database = "test.db";
my $dsn = "DBI:$driver:dbname=$database";
my $userid = "";
my $password = "";
my $dbh = DBI->connect($dsn, $userid, $password, { RaiseError => 1 })
                      or die $DBI::errstr;
print "Opened database successfully\n";

my $stmt = qq(DELETE from COMPANY where ID=2;);
my $rv = $dbh->do($stmt) or die $DBI::errstr;
if( $rv < 0 ){
   print $DBI::errstr;
}else{
   print "Total number of rows deleted : $rv\n";
}
$stmt = qq(SELECT id, name, address, salary  from COMPANY;);
my $sth = $dbh->prepare( $stmt );

$rv = $sth->execute() or die $DBI::errstr;
if($rv < 0){
   print $DBI::errstr;
}
while(my @row = $sth->fetchrow_array()) {
      print "ID = ". $row[0] . "\n";
      print "NAME = ". $row[1] ."\n";
      print "ADDRESS = ". $row[2] ."\n";
      print "SALARY =  ". $row[3] ."\n\n";
}
print "Operation done successfully\n";
$dbh->disconnect();