php - Doctrine query with nullable/optional join -


i got method on repository class me article join (category, image ...) , not every article have categories or image, don't give me expected result, cause current repository function return article have categories , image not null , ignore having null value.

my article entity have following relationship.

 /**  * @orm\manytomany(targetentity="app\articlebundle\entity\category", cascade={"persist"})  */ private $categories;  /**  * @orm\manytoone(targetentity="app\articlebundle\entity\image", cascade={"persist"})  *   */ private $image;

and repository function

public function getarticle($id) {     $qb = $this->createquerybuilder('a')     ->where('a.id = :theid')         ->setparameter('theid', $id)     ->join('a.author', 'auth')         ->addselect('auth')     ->join('a.categories', 'cat')         ->addselect('cat')     ->join('a.image', 'img')         ->addselect('img');      return $qb->getquery()->getoneornullresult(); }

now want know if can article have categories, image or not in 1 query join. want when using doctrine lazy loading (by avoid join in query) expected result.

use ->leftjoin() article have categories, image or not in 1 query:

public function getarticle($id) {     $qb = $this         ->createquerybuilder('a')         ->addselect('auth', 'cat', 'img')         ->join('a.author', 'auth')         ->leftjoin('a.categories', 'cat')         ->leftjoin('a.image', 'img')         ->where('a.id = :theid')         ->setparameter('theid', $id)     ;      return $qb->getquery()->getoneornullresult(); }

thus, avoids queries when doctrine try load related properties in lazy way.

explanation:

using ->join() or ->innerjoin():

enter image description here

this simplest, understood join , common. query return of records in left table (table a) have matching record in right table (table b).

using ->leftjoin():

enter image description here

this query return of records in left table (table a) regardless if of records have match in right table (table b). return matching records right table.

source: visual-representation-of-sql-joins explained in detail c.l. moffatt


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