DBIx::Simple
INSTALLATION
To install this module type the following:
perl Makefile.PL
make
make test
make install
Or use CPANPLUS to automate the process.
Module documentation:
NAME
DBIx::Simple - Easy-to-use OO interface to DBI, capable of emulating
subqueries
SYNOPSIS
OVERVIEW
DBIx::Simple
$db = DBIx::Simple->connect(...) # or ->new
$db->omniholder $db->emulate_subqueries # or ->esq
$db->begin_work $db->commit
$db->rollback $db->disconnect
$db->func(...)
$result = $db->query(...)
DBIx::Simple::Result
@row = $result->list @rows = $result->flat
$row = $result->array @rows = $result->arrays
$row = $result->hash @rows = $result->hashes
%map = $result->map_arrays(...)
%map = $result->map_hashes(...)
%map = $result->map
$rows = $result->rows
$result->finish
EXAMPLES
General
#!/usr/bin/perl -w
use strict;
use DBIx::Simple;
# Instant database with DBD::SQLite
my $db = DBIx::Simple->connect('dbi:SQLite:dbname=file.dat');
# Connecting to a MySQL database
my $db = DBIx::Simple->connect(
'DBI:mysql:database=test', # DBI source specification
'test', 'test', # Username and password
{ RaiseError => 1 } # Additional options
);
# Using an existing database handle
my $db = DBIx::Simple->connect($dbh);
# Abstracted example: $db->query($query, @variables)->what_you_want;
$db->commit or die $db->error;
Simple Queries
$db->query('DELETE FROM foo WHERE id = ?', $id) or die $db->error;
for (1..100) {
$db->query(
'INSERT INTO randomvalues VALUES (?, ?)',
int rand(10),
int rand(10)
) or die $db->error;
}
$db->query(
'INSERT INTO sometable VALUES (??)',
$first, $second, $third, $fourth, $fifth, $sixth
);
# (??) is expanded to (?, ?, ?, ?, ?, ?) automatically
Single row queries
my ($two) = $db->query('SELECT 1 + 1')->list;
my ($three, $four) = $db->query('SELECT 3, 2 + 2')->list;
my ($name, $email) = $db->query(
'SELECT name, email FROM people WHERE email = ? LIMIT 1',
$mail
)->list;
Fetching all rows in one go
One big flattened list (primarily for single column queries)
my @names = $db->query('SELECT name FROM people WHERE id > 5')->flat;
Rows as array references
for my $row ($db->query('SELECT name, email FROM people')->arrays) {
print "Name: $row->[0], Email: $row->[1]\n";
}
Rows as hash references
for my $row ($db->query('SELECT name, email FROM people')->hashes) {
print "Name: $row->{name}, Email: $row->{email}\n";
}
Fetching one row at a time
Rows as lists
{
my $result = $db->query('SELECT name, email FROM people');
while (my @row = $result->list) {
print "Name: $row[0], Email: $row[1]\n";
}
}
Rows as array references
{
my $result = $db->query('SELECT name, email FROM people');
while (my $row = $result->array) {
print "Name: $row->[0], Email: $row->[1]\n";
}
}
Rows as hash references
{
my $result = $db->query('SELECT name, email FROM people');
while (my $row = $result->hash) {
print "Name: $row->{name}, Email: $row->{email}\n";
}
}
Building maps (also fetching all rows in one go)
A hash of hashes
my $customers =
$db
-> query('SELECT id, name, location FROM people')
-> map_hashes('id');
# $customers = { $id => { name => $name, location => $location } }
A hash of arrays
my $customers =
$db
-> query('SELECT id, name, location FROM people')
-> map_arrays(0);
# $customers = { $id => [ $name, $location ] }
A hash of values (two-column queries)
my $names =
$db
-> query('SELECT id, name FROM people')
-> map;
# $names = { $id => $name }
Subquery emulation
$db->emulate_subqueries = 1;
my @projects = $db->query(q{
SELECT project_name
FROM projects
WHERE user_id = (
SELECT id
FROM users
WHERE email = ?
)
}, $email )->flat;
DESCRIPTION
DBIx::Simple provides a simplified interface to DBI, Perl's powerful
database module.
This module is aimed at rapid development and easy maintenance. Query
preparation and execution are combined in a single method, the result
object (which is a wrapper around the statement handle) provides easy
row-by-row and slurping methods.
The "query" method returns either a result object, or a dummy object.
The dummy object returns undef (or an empty list) for all methods and
when used in boolean context, is false. The dummy object lets you
postpone (or skip) error checking, but it also makes immediate error
checking a simple " $db->query(...) or die $db->{reason}".
For users of poorly equipped databases (like MySQL), DBIx::Simple
provides emulation of subqueries by interpolating intermediate results.
For users of better database systems (like SQLite and PostgreSQL), the
module provides direct access to DBI's transaction related methods.
DBIx::Simple methods
"DBIx::Simple->connect($dbh)"
"DBIx::Simple->connect($dsn, $user, $pass, \%options)"
The "connect" or "new" class method takes either an existing
DBI object ($dbh), or a list of arguments to pass to
"DBI->connect". See DBI for a detailed description.
You cannot use this method to clone a DBIx::Simple object: the
$dbh passed should be a DBI::db object, not a DBIx::Simple
object.
This method is the constructor and returns a DBIx::Simple
object on success. On failure, it returns undef.
"omniholder($new_value)"
This returns the omniholder string, after setting a new string
if one is given. Use a $new_value of "undef" or an empty
string to disable the omniholder feature. Note that the given
$new_value is not a regular expression. The default omniholder
is "(??)".
As shown in the SYNOPSIS, you can use an omniholder to avoid
having to count question marks. In a query, "(??)" (or
whatever string you set using this method) is replaced with
"(?, ?, ?, ...)", with as many question marks as @values
passed to the query method (see below).
"emulate_subqueries($bool)", "esq($bool)"
DBIx::Simple can emulate nested subqueries (SELECT only) by
executing them and interpolating the results. This methods
enables or disables this feature. Subquery emulation is
disabled by default, and should not be used if the database
provides real subqueries.
Only subqueries like "(SELECT ...)" (note the parentheses) are
interpolated.
Please note that emulation is done by doing multiple queries
and is not atomic, as it would be if the database supported
real subqueries. The queries are executed independently.
"error" Returns the error string of the last DBI method. See the
discussion of ""err"" and ""errstr"" in DBI.
"query($query, @values)"
The "query" method pepares and executes the query and returns
a result object.
If an omniholder (see above) is present in the query, it is
replaced with a list of as many question marks as @values. If
subquery emulation (see above) is enabled, subquery results
are interpolated in the main query before the main query is
executed.
The database drivers substitute placeholders (question marks
that do not appear in quoted literals) in the query with the
given @values, after them escaping them. You should always use
placeholders, and never use user input in database queries.
On success, returns a DBIx::Simple::Result object and sets
$db->{success} to 1.
On failure, returns a DBIx::Simple::Dummy object and sets
$db->{success} to 0.
"begin_work", "commit", "rollback"
These transaction related methods call the DBI respective
methods and Do What You Mean. See DBI for details.
"func(...)"
This calls the "func" method of DBI. See DBI for details.
"disconnect"
Destroys (finishes) active statements and disconnects.
Whenever the database object is destroyed, this happens
automatically. After disconnecting, you can no longer use the
database object or any of its result object.
DBIx::Simple::Dummy
The "query" method of DBIx::Simple returns a dummy object on failure.
Its methods all return an empty list or undef, depending on context.
When used in boolean context, a dummy object evaluates to false.
DBIx::Simple::Result methods
"list" Fetches a single row and returns a list of values. In scalar
context, this returns only the last value.
"array" Fetches a single row and returns an array reference.
"hash" Fetches a single row and returns a hash reference.
"flat" Fetches all remaining rows and returns a flattened list.
"arrays" Fetches all remaining rows and returns a list of array
references.
In scalar context, returns an array reference.
"hashes" Fetches all remaining rows and returns a list of hash
references.
In scalar context, returns an array reference.
"map_arrays($column_number)"
Constructs a hash of array references keyed by the values in
the chosen column.
In scalar context, returns a hash reference.
"map_hashes($column_name)"
Constructs a hash of hash references keyed by the values in
the chosen column.
In scalar context, returns a hash.
"map" Constructs a simple hash, using the first two columns as
key/value pairs. Should only be used with queries that return
two columns.
In scalar context, returns a reference to the hash.
"rows" Returns the number of rows affected by the last row affecting
command, or -1 if the number of rows is not known or not
available.
For SELECT statements, it is generally not possible to know
how many rows are returned. MySQL does provide this
information. See DBI for a detailed explanation.
"finish" Finishes the statement. After finishing a statement, it can no
longer be used. When the result object is destroyed, its
statement handle is automatically finished and destroyed.
There should be no reason to call this method explicitly; just
let the result object go out of scope.
MISCELLANEOUS
Although this module has been tested thoroughly in production
environments, it still has no automated test suite. If you want to write
tests, please contact me.
The mapping methods do not check whether the keys are unique. Rows that
are fetched later overwrite earlier ones.
PrintError is disabled by default. If you enable it, beware that it will
report line numbers in DBIx/Simple.pm.
Note: this module does not provide any SQL abstraction and never will.
If you don't want to write SQL queries, use DBIx::Abstract.
LICENSE
There is no license. This software was released into the public domain.
Do with it what you want, but on your own risk. The author disclaims any
responsibility.
AUTHOR
Juerd Waalboer <juerd@cpan.org> <http://juerd.nl/>
SEE ALSO
perl, perlref, DBI