diff --git a/docs/en/reference/dql-doctrine-query-language.rst b/docs/en/reference/dql-doctrine-query-language.rst index b0d19e8e0..1b0d3b013 100644 --- a/docs/en/reference/dql-doctrine-query-language.rst +++ b/docs/en/reference/dql-doctrine-query-language.rst @@ -49,10 +49,6 @@ SELECT queries DQL SELECT clause ~~~~~~~~~~~~~~~~~ -The select clause of a DQL query specifies what appears in the -query result. The composition of all the expressions in the select -clause also influences the nature of the query result. - Here is an example that selects all users with an age > 20: .. code-block:: php @@ -83,14 +79,58 @@ Lets examine the query: The result of this query would be a list of User objects where all users are older than 20. -The SELECT clause allows to specify both class identification -variables that signal the hydration of a complete entity class or -just fields of the entity using the syntax ``u.name``. Combinations -of both are also allowed and it is possible to wrap both fields and -identification values into aggregation and DQL functions. Numerical -fields can be part of computations using mathematical operations. -See the sub-section on `Functions, Operators, Aggregates`_ for -more information. +Result format +~~~~~~~~~~~~~ +The composition of the expressions in the SELECT clause also +influences the nature of the query result. There are three +cases: + +**All objects** + +.. code-block:: sql + + SELECT u, p, n FROM Users u... + +In this case, the result will be an array of User objects because of +the FROM clause, with children ``p`` and ``n`` hydrated because of +their inclusion in the SELECT clause. + +**All scalars** + +.. code-block:: sql + + SELECT u.name, u.address FROM Users u... + +In this case, the result will be an array of arrays. In the example +above, each element of the result array would be an array of the +scalar name and address values. + +You can select scalars from any entity in the query. + +**Mixed** + +.. code-block:: sql + + ``SELECT u, p.quantity FROM Users u...`` + +Here, the result will again be an array of arrays, with each element +being an array made up of a User object and the scalar value +``p.quantity``. + +Multiple FROM clauses are allowed, which would cause the result +array elements to cycle through the classes included in the +multiple FROM clauses. + +.. note:: + + You cannot select other entities unless you also select the + root of the selection (which is the first entity in FROM). + + For example, ``SELECT p,n FROM Users u...`` would be wrong because + ``u`` is not part of the SELECT + + Doctrine throws an exception if you violate this constraint. + Joins ~~~~~ @@ -319,7 +359,8 @@ article-ids: $query = $em->createQuery('SELECT u.id, a.id as article_id FROM CmsUser u LEFT JOIN u.articles a'); $results = $query->getResult(); // array of user ids and every article_id for each user -Restricting a JOIN clause by additional conditions: +Restricting a JOIN clause by additional conditions specified by +WITH: .. code-block:: php @@ -452,6 +493,18 @@ Joins between entities without associations were not possible until version createQuery('SELECT u FROM User u JOIN Blacklist b WITH u.email = b.email'); +.. note:: + The differences between WHERE, WITH and HAVING clauses may be + confusing. + + - WHERE is applied to the results of an entire query + - WITH is applied to a join as an additional condition. For + arbitrary joins (SELECT f, b FROM Foo f, Bar b WITH f.id = b.id) + the WITH is required, even if it is 1 = 1 + - HAVING is applied to the results of a query after + aggregation (GROUP BY) + + Partial Object Syntax ^^^^^^^^^^^^^^^^^^^^^ @@ -607,6 +660,9 @@ The same restrictions apply for the reference of related entities. Functions, Operators, Aggregates -------------------------------- +It is possible to wrap both fields and identification values into +aggregation and DQL functions. Numerical fields can be part of +computations using mathematical operations. DQL Functions ~~~~~~~~~~~~~ @@ -1381,11 +1437,11 @@ Given that there are 10 users and corresponding addresses in the database the ex .. note:: Changing the fetch mode during a query mostly makes sense for one-to-one and many-to-one relations. In that case, -   all the necessary IDs are available after the root entity (``user`` in the above example) has been loaded. So, one -   query per association can be executed to fetch all the referred-to entities (``address``). + all the necessary IDs are available after the root entity (``user`` in the above example) has been loaded. So, one + query per association can be executed to fetch all the referred-to entities (``address``). For one-to-many relations, changing the fetch mode to eager will cause to execute one query **for every root entity -   loaded**. This gives no improvement over the ``lazy`` fetch mode which will also initialize the associations on + loaded**. This gives no improvement over the ``lazy`` fetch mode which will also initialize the associations on a one-by-one basis once they are accessed.