NAME
SQL::DB - Perl interface to SQL Databases
VERSION
0.10. Development release.
SYNOPSIS
use SQL::DB qw(define_tables count max);
define_tables(
[
table => 'addresses',
class => 'Address',
column => [name => 'id', type => 'INTEGER', primary => 1],
column => [name => 'kind', type => 'INTEGER'],
column => [name => 'city', type => 'INTEGER'],
],
[
table => 'persons',
class => 'Person',
column => [name => 'id', type => 'INTEGER', primary => 1],
column => [name => 'name', type => 'VARCHAR(255)'],
column => [name => 'age', type => 'INTEGER'],
column => [name => 'address', type => 'INTEGER',
ref => 'addresses(id)',
null => 1],
column => [name => 'parent', type => 'INTEGER',
ref => 'persons(id)',
null => 1],
index => 'name',
]
);
my $db = SQL::DB->new();
$db->connect('dbi:SQLite:/tmp/sqldbtest.db', 'user', 'pass', {});
$db->deploy;
my $persons = $db->arow('persons');
my $addresses = $db->arow('addresses');
$db->do(
insert => [$persons->id, $persons->name, $persons->age],
values => [1, 'Homer', 43],
);
$db->do(
insert => [$addresses->id, $addresses->kind, $addresses->city],
values => [2, 'residential', 'Springfield'], # Pg: [nextval('id')...
);
$db->do(
update => [$persons->set_address(2)],
where => $persons->name == 'Homer',
);
my $ans = $db->fetch1(
select => [count($persons->name)->as('count_name'),
max($persons->age)->as('max_age')],
from => $persons,
where => $persons->age > 40,
);
# The following prints "Head count: 1 Max age:43"
print 'Head count: '. $ans->count_name .
' Max age: '. $ans->max_age ."\n";
my @items = $db->fetch(
select => [$persons->name, $persons->age, $addresses->city],
from => $persons,
left_join => $addresses,
on => $addresses->id == $persons->address,
where => ($addresses->city == 'Springfield') & ($persons->age > 40),
order_by => $persons->age->desc,
limit => 10,
);
# Give me "Homer(43) lives in Springfield"
foreach my $item (@items) {
print $item->name, '(',$item->age,') lives in ', $item->city, "\n";
}
return @items # this line for the automatic testDESCRIPTION
SQL::DB provides a low-level interface to SQL databases, using Perl objects and logic operators. It is NOT an Object Relational Mapper like Class::DBI and neither is it an abstraction such as SQL::Abstract. It falls somewhere inbetween.
After using define_tables() to specify your schema and creating an SQL::DB object, the typical workflow is as follows:
* connect() to the database
* deploy() the schema (CREATE TABLEs etc)
* Using one or more "abstract rows" obtained via arow() you can do() insert, update or delete queries.
* Using one or more "abstract rows" obtained via arow() you can fetch() (select) data to work with (and possibly modify).
* Repeat the above three steps as needed. Further queries (with a higher level of automation) are possible with the objects returned by fetch().
* disconnect() from the database.
SQL::DB is capable of generating just about any kind of query, including, but not limited to, JOINs, nested SELECTs, UNIONs, database-side operator invocations, function calls, aggregate expressions, etc. However this package is still quite new, and nowhere near complete. Feedback, testing, and (even better) patches are all welcome.
For a more complete introduction see SQL::DB::Intro.
CLASS SUBROUTINES
define_tables(@definitions)
Define the structure of tables, their columns, and associated indexes. @definition is list of ARRAY references as required by SQL::DB::Schema::Table. This class subroutine can be called multiple times. Will warn if you redefine a table.
METHODS
new(@names)
Create a new SQL::DB object. The optional @names lists the tables that this object is to know about. By default all tables defined by define_tables() are known.
connect($dbi, $user, $pass, $attrs)
Connect to a database. The parameters are passed directly to DBI->connect. This method also informs the internal table/column representations what type of database we are connected to, so they can set their database-specific features accordingly.
connect_cached($dbi, $user, $pass, $attrs)
Connect to a database, potentially reusing an existing connection. The parameters are passed directly to DBI->connect_cached. Useful when running under persistent environments. This method also informs the internal table/column representations what type of database we are connected to, so they can set their database-specific features accordingly.
dbh
Returns the DBI database handle we are connected with.
deploy
Runs the CREATE TABLE and CREATE INDEX statements necessary to create the schema in the database. Will warn on any tables that already exist. Table creation is automatically ordered based on column references.
query(@query)
Return an SQL::DB::Schema::Query object as defined by @query. This method is useful when creating nested SELECTs, UNIONs, or you can print the returned object if you just want to see what the SQL looks like.
query_as_string($sql, @bind_values)
An internal function for pretty printing SQL queries by inserting the bind values into the SQL itself. Returns a string.
do(@query)
Constructs a SQL::DB::Schema::Query object as defined by @query and runs that query against the connected database. Croaks if an error occurs. This is the method to use for any statement that doesn't retrieve values (eg INSERT, UPDATE and DELETE). Returns whatever value the underlying DBI->do call returns.
fetch(@query)
Constructs an SQL::DB::Schema::Query object as defined by @query and runs that query against the connected database. Croaks if an error occurs. This method should be used for SELECT-type statements that retrieve rows.
When called in array context returns a list of objects based on SQL::DB::Row. The objects have accessors for each column in the query. Be aware that this can consume large amounts of memory if there are lots of rows retrieved.
When called in scalar context returns a query cursor (SQL::DB::Cursor) (with "next", "all" and "reset" methods) to retrieve dynamically constructed objects one at a time.
fetch1(@query)
Similar to fetch() but always returns only the first object from the result set. All other rows (if any) can not be retrieved. You should only use this method if you know/expect one result.
qcount
Returns the number of successful queries that have been run.
create_seq($name)
This (and the seq() method below) are the only attempt that SQL::DB makes at cross-database abstraction. create_seq() creates a sequence called $name. The sequence is actually just a row in the 'sqldb' table.
Warns if the sequence already exists, returns true if successful.
seq($name,$count)
Return the next value for the sequence $name. If $count is specified then a list/array of $count values are returned. The uniqueness of the returned value(s) is assured by locking the appropriate table (or rows in the table) as required.
Note that this is not intended as a replacment for auto-incrementing primary keys in MySQL/SQLite, or real sequences in PostgreSQL. It is simply an ease-of-use mechanism for applications wishing to use a common sequence api across multiple databases.
disconnect
Disconnect from the database. Effectively DBI->disconnect.
METHODS ON FETCHED OBJECTS
Although SQL::DB is not an ORM system it does comes with a very thin object layer. Objects returned by fetch() and fetch1() can be modified using their set_* methods, just like a regular ORM system. However, the difference here is that the objects fields may map across multiple database tables.
Since the objects keep track of which columns have changed, and they also know which columns belong to which tables and which columns are primary keys, they can also automatically generate the appropriate commands for UPDATE or DELETE statements in order to make matching changes in the database.
Of course, the appropriate statements only work if the primary keys have been included as part of the fetch(). See the q_update() and q_delete() methods in SQL::DB::Row for more details.
update($sqlobject)
Nearly the same as $db->do($sqlobject->q_update).
delete($sqlobject)
Nearly the same as $db->do($sqlobject->q_delete).
insert($sqlobject)
Nearly the same as $db->do($sqlobject->q_insert).
DEBUGGING
If $SQL::DB::DEBUG is set to a true value then SQL queries and other important actions are 'warn'ed to STDERR
SEE ALSO
SQL::Abstract, DBIx::Class, Class::DBI, Tangram
You can see SQL::DB in action in the MySpam application, also by the same author.
AUTHOR
Mark Lawrence <nomad@null.net>
COPYRIGHT AND LICENSE
Copyright (C) 2007 Mark Lawrence <nomad@null.net>
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.