Sélection d'une base de données avec JDatabase

From Joomla! Documentation

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3.x
Joomla! 
2.5
Note de version

Remarque : de nombreux exemples présentés ci-dessous utilisent $db->query() au lieu de $db->execute(). C'est une méthode ancienne utilisée dans Joomla! 1.5 et 2.5 et est un obsolète depuis Joomla! 3.x.

Ce didacticiel est divisé en deux parties indépendantes :

  • L'insertion, la mise à jour et la suppression de données de la base de données.
  • La sélection des données à partir d'une ou plusieurs tables et la récupération sous différentes formes.

This section of the documentation looks at selecting data from a database table and retrieving it in a variety of formats. To see the other part click here

Introduction

Joomla! propose un système sophistiqué de couche d'abstraction de base de données pour en simplifier l'utilisation par les développeurs d'extensions tierces. Les nouvelles versions de la Plateforme d'API Joomla! proposent des fonctionnalités supplémentaires qui permettent d'étendre encore plus la couche de base de données et inclues des fonctionnalités telles que des connecteurs pour une plus grande variété de serveurs de base de données ou encore le chaînage de requêtes pour améliorer la lisibilité des codes de connexion et pour simplifier le codage SQL.

Joomla permet l'utilisation de différents types de systèmes de base de données d'exécution SQL et peut être utilisé sur une grande variété d'environnements différents avec différents préfixes de table. En plus de ces fonctionnalités, la classe crée automatiquement la connexion à la base de données. Il suffit de deux lignes de code pour l'instanciation de l'objet dont vous avez et obtenir un résultat à partir de la base de données dans différents formats. Grace à la couche de base de données, Joomla assure un maximum de compatibilité et de flexibilité pour vos extensions.

La requête

Joomla's database querying changed with the introduction of Joomla 1.6. The recommended way of building database queries is through "query chaining" (although string queries are still supported).

Le chaînage de requêtes fait référence à une méthode permettant la connexion à un certain nombre de méthodes, les unes après les autres où chaque méthode retournant un objet peut prendre en charge la nouvelle méthode, améliorant ainsi la lisibilité et la simplification du code.

Pour obtenir une nouvelle instance de la classe JDatabaseQuery, nous utilisons la méthode JDatabaseDriver getQuery :

$db = JFactory::getDbo();

$query = $db->getQuery(true);

JDatabaseDriver::getQuery peut prendre un argument optionnel, $new, ce qui peut être true (vrai) ou false (faux) (la valeur par défaut est false).

Pour interroger notre source de données, nous pouvons faire appel à un certain nombre de méthodes JDatabaseQuery. Ces méthodes vont encapsuler la requête des données sources (SQL) en cachant la syntaxe spécifique de la requête du développeur et augmenter ainsi la portabilité du code source du développeur.

Les méthodes les plus fréquemment utilisées comprennent : select, from, join, where et order. Il existe également d'autres méthodes telles que insert, update et delete pour modifier des enregistrements dans la base de données. En chaînant ces méthodes d'appel à d'autres, vous pouvez créer presque n'importe quelle requête à votre base de données sans compromettre la portabilité de votre code..

Sélectionner des enregistrements dans une table unique

Ci-dessous un exemple de création d'une requête de base de données utilisant la classe JDatabaseQuery. À l'aide des méthodes select, from, where et order, il est possible de créer des requêtes flexibles et lisibles :

// Get a db connection.
$db = JFactory::getDbo();

// Create a new query object.
$query = $db->getQuery(true);

// Select all records from the user profile table where key begins with "custom.".
// Order it by the ordering field.
$query->select($db->quoteName(array('user_id', 'profile_key', 'profile_value', 'ordering')));
$query->from($db->quoteName('#__user_profiles'));
$query->where($db->quoteName('profile_key') . ' LIKE '. $db->quote('\'custom.%\''));
$query->order('ordering ASC');

// Reset the query using our newly populated query object.
$db->setQuery($query);

// Load the results as a list of stdClass objects (see later for more options on retrieving data).
$results = $db->loadObjectList();

La requête peut également être chaînée pour la simplifier davantage :

$query
    ->select($db->quoteName(array('user_id', 'profile_key', 'profile_value', 'ordering')))
    ->from($db->quoteName('#__user_profiles'))
    ->where($db->quoteName('profile_key') . ' LIKE '. $db->quote('\'custom.%\''))
    ->order('ordering ASC');

Le chaînage peut être utile lorsque les requêtes deviennent plus longs et plus complexes.

Le groupement peut également être réalisé simplement. La requête suivante compterait le nombre d'articles dans chaque catégorie.

$query
    ->select( array('catid', 'COUNT(*)') )
    ->from($db->quoteName('#__content'))
    ->group($db->quoteName('catid'));

Une limite pour une requête peut être définie avec setLimit. Par exemple, dans la requête suivante, jusqu'à 10 enregistrements seront retournés.

$query
    ->select($db->quoteName(array('user_id', 'profile_key', 'profile_value', 'ordering')))
    ->from($db->quoteName('#__user_profiles'))
    ->setLimit('10');

Sélectionner des enregistrements dans plusieurs tables

Using the JDatabaseQuery's join methods, we can select records from multiple related tables. The generic "join" method takes two arguments; the join "type" (inner, outer, left, right) and the join condition. In the following example you will notice that we can use all of the keywords we would normally use if we were writing a native SQL query, including the AS keyword for aliasing tables and the ON keyword for creating relationships between tables. Also note that the table alias is used in all methods which reference table columns (I.e. select, where, order).

// Get a db connection.
$db = JFactory::getDbo();

// Create a new query object.
$query = $db->getQuery(true);

// Select all articles for users who have a username which starts with 'a'.
// Order it by the created date.
// Note by putting 'a' as a second parameter will generate `#__content` AS `a`
$query
    ->select(array('a.*', 'b.username', 'b.name'))
    ->from($db->quoteName('#__content', 'a'))
    ->join('INNER', $db->quoteName('#__users', 'b') . ' ON (' . $db->quoteName('a.created_by') . ' = ' . $db->quoteName('b.id') . ')')
    ->where($db->quoteName('b.username') . ' LIKE \'a%\'')
    ->order($db->quoteName('a.created') . ' DESC');

// Reset the query using our newly populated query object.
$db->setQuery($query);

// Load the results as a list of stdClass objects (see later for more options on retrieving data).
$results = $db->loadObjectList();

The join method above enables us to query both the content and user tables, retrieving articles with their author details. There are also convenience methods for joins:

Nous pouvons utiliser plusieurs jonctions pour opérer une requête pour plus de deux tables :

$query
    ->select(array('a.*', 'b.username', 'b.name', 'c.*', 'd.*'))
    ->from($db->quoteName('#__content', 'a'))
    ->join('INNER', $db->quoteName('#__users', 'b') . ' ON (' . $db->quoteName('a.created_by') . ' = ' . $db->quoteName('b.id') . ')')
    ->join('LEFT', $db->quoteName('#__user_profiles', 'c') . ' ON (' . $db->quoteName('b.id') . ' = ' . $db->quoteName('c.user_id') . ')')
    ->join('RIGHT', $db->quoteName('#__categories', 'd') . ' ON (' . $db->quoteName('a.catid') . ' = ' . $db->quoteName('d.id') . ')')
    ->where($db->quoteName('b.username') . ' LIKE \'a%\'')
    ->order($db->quoteName('a.created') . ' DESC');

Remarquez comment le chaînage rend le code source plus lisible pour ces longues requêtes.

In some cases, you will also need to use the AS clause when selecting items to avoid column name conflicts. In this case, multiple select statements can be chained in conjunction with using the second parameter of $db->quoteName.

$query
    ->select('a.*')
    ->select($db->quoteName('b.username', 'username'))
    ->select($db->quoteName('b.name', 'name'))
    ->from($db->quoteName('#__content', 'a'))
    ->join('INNER', $db->quoteName('#__users', 'b') . ' ON (' . $db->quoteName('a.created_by') . ' = ' . $db->quoteName('b.id') . ')')
    ->where($db->quoteName('b.username') . ' LIKE \'a%\'')
    ->order($db->quoteName('a.created') . ' DESC');

A second array can also be used as the second parameter of the select statement to populate the values of the AS clause. Remember to include nulls in the second array to correspond to columns in the first array that you don't want to use the AS clause for:

$query
    ->select(array('a.*'))
    ->select($db->quoteName(array('b.username', 'b.name'), array('username', 'name')))
    ->from($db->quoteName('#__content', 'a'))
    ->join('INNER', $db->quoteName('#__users', 'b') . ' ON (' . $db->quoteName('a.created_by') . ' = ' . $db->quoteName('b.id') . ')')
    ->where($db->quoteName('b.username') . ' LIKE \'a%\'')
    ->order($db->quoteName('a.created') . ' DESC');


Résultats de la requête

La classe database proposent différentes méthodes pour pouvoir travailler avec un ensemble de résultats d'une requête.

Valeur unique de résultat

loadResult()

Use loadResult() when you expect just a single value back from your database query.

id nom email nom d'utilisateur
1 John Smith johnsmith@domaine.exemple johnsmith
2 Magda Hellman magda_h@domaine.exemple magdah
3 Yvonne de Gaulle ydg@domaine.exemple ydegaulle

This is often the result of a 'count' query to get a number of records:

$db = JFactory::getDbo();
$query = $db->getQuery(true);
$query->select('COUNT(*)');
$query->from($db->quoteName('#__my_table'));
$query->where($db->quoteName('name')." = ".$db->quote($value));

// Reset the query using our newly populated query object.
$db->setQuery($query);
$count = $db->loadResult();

or where you are just looking for a single field from a single row of the table (or possibly a single field from the first row returned).

$db = JFactory::getDbo();
$query = $db->getQuery(true);
$query->select('field_name');
$query->from($db->quoteName('#__my_table'));
$query->where($db->quoteName('some_name')." = ".$db->quote($some_value));

$db->setQuery($query);
$result = $db->loadResult();


Single Row Results

Each of these results functions will return a single record from the database even though there may be several records that meet the criteria that you have set. To get more records you need to call the function again.

id nom email nom d'utilisateur
1 John Smith johnsmith@domaine.exemple johnsmith
2 Magda Hellman magda_h@domaine.exemple magdah
3 Yvonne de Gaulle ydg@domaine.exemple ydegaulle

loadRow()

loadRow() returns an indexed array from a single record in the table:

. . .
$db->setQuery($query);
$row = $db->loadRow();
print_r($row);

donnera :

Array ( [0] => 1, [1] => John Smith, [2] => johnsmith@domain.example, [3] => johnsmith ) 
You can access the individual values by using:
$row['index'] // e.g. $row['2']

Remarques :

  1. The array indices are numeric starting from zero.
  2. Whilst you can repeat the call to get further rows, one of the functions that returns multiple rows might be more useful.

loadAssoc()

loadAssoc() returns an associated array from a single record in the table:

. . .
$db->setQuery($query);
$row = $db->loadAssoc();
print_r($row);

will give:

Array ( [id] => 1, [name] => John Smith, [email] => johnsmith@domain.example, [username] => johnsmith )
You can access the individual values by using:
$row['name'] // e.g. $row['email']

Notes:

  1. Whilst you can repeat the call to get further rows, one of the functions that returns multiple rows might be more useful.

loadObject()

loadObject returns a PHP object from a single record in the table:

. . .
$db->setQuery($query);
$result = $db->loadObject();
print_r($result);

will give:

stdClass Object ( [id] => 1, [name] => John Smith, [email] => johnsmith@domain.example, [username] => johnsmith )
You can access the individual values by using:
$result->index // e.g. $result->email

Notes:

  1. Whilst you can repeat the call to get further rows, one of the functions that returns multiple rows might be more useful.

Single Column Results

Each of these results functions will return a single column from the database.

id nom email nom d'utilisateur
1 John Smith johnsmith@domaine.exemple johnsmith
2 Magda Hellman magda_h@domaine.exemple magdah
3 Yvonne de Gaulle ydg@domaine.exemple ydegaulle

loadColumn()

loadColumn() returns an indexed array from a single column in the table:

$query->select('name'));
      ->from . . .";
. . .
$db->setQuery($query);
$column= $db->loadColumn();
print_r($column);

donnera :

Array ( [0] => John Smith, [1] => Magda Hellman, [2] => Yvonne de Gaulle )
You can access the individual values by using:
$column['index'] // e.g. $column['2']

Notes:

  1. The array indices are numeric starting from zero.
  2. loadColumn() is equivalent to loadColumn(0).

loadColumn($index)

loadColumn($index) returns an indexed array from a single column in the table:

$query->select(array('name', 'email', 'username'));
      ->from . . .";
. . .
$db->setQuery($query);
$column= $db->loadColumn(1);
print_r($column);

will give:

Array ( [0] => johnsmith@domain.example, [1] => magda_h@domain.example, [2] => ydg@domain.example )
You can access the individual values by using:
$column['index'] // e.g. $column['2']

loadColumn($index) allows you to iterate through a series of columns in the results

. . .
$db->setQuery($query);
for ( $i = 0; $i <= 2; $i++ ) {
  $column= $db->loadColumn($i);
  print_r($column);
}

will give:

Array ( [0] => John Smith, [1] => Magda Hellman, [2] => Yvonne de Gaulle ),
Array ( [0] => johnsmith@domain.example, [1] => magda_h@domain.example, [2] => ydg@domain.example ),
Array ( [0] => johnsmith, [1] => magdah, [2] => ydegaulle )

Notes:

  1. The array indices are numeric starting from zero.

Multi-Row Results

Each of these results functions will return multiple records from the database.

id name email nom d'utilisateur
1 John Smith johnsmith@domain.example johnsmith
2 Magda Hellman magda_h@domain.example magdah
3 Yvonne de Gaulle ydg@domain.example ydegaulle

loadRowList()

loadRowList() returns an indexed array of indexed arrays from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadRowList();
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[0] => Array ( [0] => 1, [1] => John Smith, [2] => johnsmith@domain.example, [3] => johnsmith ), 
[1] => Array ( [0] => 2, [1] => Magda Hellman, [2] => magda_h@domain.example, [3] => magdah ), 
[2] => Array ( [0] => 3, [1] => Yvonne de Gaulle, [2] => ydg@domain.example, [3] => ydegaulle ) 
)
You can access the individual rows by using:
$row['index'] // e.g. $row['2']
and you can access the individual values by using:
$row['index']['index'] // e.g. $row['2']['3']

Notes:

  1. The array indices are numeric starting from zero.

loadAssocList()

loadAssocList() returns an indexed array of associated arrays from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadAssocList();
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[0] => Array ( [id] => 1, [name] => John Smith, [email] => johnsmith@domain.example, [username] => johnsmith ), 
[1] => Array ( [id] => 2, [name] => Magda Hellman, [email] => magda_h@domain.example, [username] => magdah ), 
[2] => Array ( [id] => 3, [name] => Yvonne de Gaulle, [email] => ydg@domain.example, [username] => ydegaulle ) 
) 
You can access the individual rows by using:
$row['index'] // e.g. $row['2']
and you can access the individual values by using:
$row['index']['column_name'] // e.g. $row['2']['email']

loadAssocList($key)

loadAssocList('key') returns an associated array - indexed on 'key' - of associated arrays from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadAssocList('username');
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[johnsmith] => Array ( [id] => 1, [name] => John Smith, [email] => johnsmith@domain.example, [username] => johnsmith ), 
[magdah] => Array ( [id] => 2, [name] => Magda Hellman, [email] => magda_h@domain.example, [username] => magdah ), 
[ydegaulle] => Array ( [id] => 3, [name] => Yvonne de Gaulle, [email] => ydg@domain.example, [username] => ydegaulle ) 
)
You can access the individual rows by using:
$row['key_value'] // e.g. $row['johnsmith']
and you can access the individual values by using:
$row['key_value']['column_name'] // e.g. $row['johnsmith']['email']

Note: Key must be a valid column name from the table; it does not have to be an Index or a Primary Key. But if it does not have a unique value you may not be able to retrieve results reliably.

loadAssocList($key, $column)

loadAssocList('key', 'column') returns an associative array, indexed on 'key', of values from the column named 'column' returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadAssocList('id', 'username');
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[1] => John Smith, 
[2] => Magda Hellman, 
[3] => Yvonne de Gaulle,
)

Note: Key must be a valid column name from the table; it does not have to be an Index or a Primary Key. But if it does not have a unique value you may not be able to retrieve results reliably.

loadObjectList()

loadObjectList() returns an indexed array of PHP objects from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadObjectList();
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[0] => stdClass Object ( [id] => 1, [name] => John Smith, 
    [email] => johnsmith@domain.example, [username] => johnsmith ), 
[1] => stdClass Object ( [id] => 2, [name] => Magda Hellman, 
    [email] => magda_h@domain.example, [username] => magdah ), 
[2] => stdClass Object ( [id] => 3, [name] => Yvonne de Gaulle, 
    [email] => ydg@domain.example, [username] => ydegaulle ) 
)
You can access the individual rows by using:
$row['index'] // e.g. $row['2']
and you can access the individual values by using:
$row['index']->name // e.g. $row['2']->email

loadObjectList($key)

loadObjectList('key') returns an associated array - indexed on 'key' - of objects from the table records returned by the query:

. . .
$db->setQuery($query);
$row = $db->loadObjectList('username');
print_r($row);

will give (with line breaks added for clarity):

Array ( 
[johnsmith] => stdClass Object ( [id] => 1, [name] => John Smith, 
    [email] => johnsmith@domain.example, [username] => johnsmith ), 
[magdah] => stdClass Object ( [id] => 2, [name] => Magda Hellman, 
    [email] => magda_h@domain.example, [username] => magdah ), 
[ydegaulle] => stdClass Object ( [id] => 3, [name] => Yvonne de Gaulle, 
    [email] => ydg@domain.example, [username] => ydegaulle ) 
)
You can access the individual rows by using:
$row['key_value'] // e.g. $row['johnsmith']
and you can access the individual values by using:
$row['key_value']->column_name // e.g. $row['johnsmith']->email

Note: Key must be a valid column name from the table; it does not have to be an Index or a Primary Key. But if it does not have a unique value you may not be able to retrieve results reliably.

Miscellaneous Result Set Methods

getNumRows()

getNumRows() will return the number of result rows found by the last SELECT or SHOW query and waiting to be read. To get a result from getNumRows() you have to run it after the query and before you have retrieved any results. To retrieve the number of rows affected by a INSERT, UPDATE, REPLACE or DELETE query, use getAffectedRows().

. . .
$db->setQuery($query);
$db->execute();
$num_rows = $db->getNumRows();
print_r($num_rows);
$result = $db->loadRowList();
donnera :
3

Note: getNumRows() is only valid for statements like SELECT or SHOW that return an actual result set. If you run getNumRows() after loadRowList() - or any other retrieval method - you will get a PHP Warning:

Warning: mysql_num_rows(): 80 is not a valid MySQL result resource 
in libraries\joomla\database\database\mysql.php on line 344

See also