Doctrine_manual-1-2-en

Chapter 9: DQL (Doctrine Query Language) 130
JOIN ] [ON | WITH] [INDEXBY]
,
[[LEFT | INNER] JOIN ] [ON | WITH]
[INDEXBY] ,
...
[[LEFT | INNER] JOIN ] [ON | WITH]
[INDEXBY]
DQL supports two kinds of joins INNER JOINs and LEFT JOINs. For each joined component,
you can optionally specify an alias.
The default join type is LEFT JOIN. This join can be indicated by the use of either LEFT
JOIN clause or simply ',', hence the following queries are equal:
Listing
9-43
// test.php
// ...
$q = Doctrine_Query::create()
->select('u.id, p.id')
->from('User u')
->leftJoin('u.Phonenumbers p');
$q = Doctrine_Query::create()
->select('u.id, p.id')
->from('User u, u.Phonenumbers p');
echo $q->getSqlQuery();
The recommended form is the first because it is more verbose and easier to read and
understand what is being done.
The above call to getSql() would output the following SQL query:
Listing
9-44
SELECT
u.id AS u__id,
p.id AS p__id
FROM user u
LEFT JOIN phonenumber p ON u.id = p.user_id
Notice how the JOIN condition is automatically added for you. This is because Doctrine
knows how User and Phonenumber are related so it is able to add it for you.
INNER JOIN produces an intersection between two specified components (that is, each and
every record in the first component is joined to each and every record in the second
component). So basically INNER JOIN can be used when you want to efficiently fetch for
example all users which have one or more phonenumbers.
By default DQL auto-adds the primary key join condition:
Listing
9-45
// test.php
// ...
$q = Doctrine_Query::create()
->select('u.id, p.id')
->from('User u')
->leftJoin('u.Phonenumbers p');
----------------- Brought to you by