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Web & App Development

The Query

Joomla's database querying has changed since the new Joomla Framework was introduced "query chaining" is now the recommended method for building database queries (although string queries are still supported).

Query chaining refers to a method of connecting a number of methods, one after the other, with each method returning an object that can support the next method, improving readability and simplifying code.

To obtain a new instance of the JDatabaseQuery class we use the JDatabaseDriver getQuery method:

$db = JFactory::getDbo();
$query = $db->getQuery(true);

The JDatabaseDriver::getQuery takes an optional argument, $new, which can be true or false (the default being false).

To query our data source we can call a number of JDatabaseQuery methods; these methods encapsulate the data source's query language (in most cases SQL), hiding query-specific syntax from the developer and increasing the portability of the developer's source code.

Some of the more frequently used methods include; select, from, join, where and order. There are also methods such as insert, update and delete for modifying records in the data store. By chaining these and other method calls, you can create almost any query against your data store without compromising portability of your code.

Inserting a Record

Using SQL

The JDatabaseQuery class provides a number of methods for building insert queries, the most common being insert, columns and values.

// Get a db connection.
$db = JFactory::getDbo();
// Create a new query object.
$query = $db->getQuery(true);
// Insert columns.
$columns = array('user_id', 'profile_key', 'profile_value', 'ordering');
// Insert values.
$values = array(1001, $db->quote('custom.message'), $db->quote('Inserting a record using insert()'), 1);
// Prepare the insert query.
    ->values(implode(',', $values));
// Set the query using our newly populated query object and execute it.

Using an Object

The JDatabaseDriver class also provides a convenient method for saving an object directly to the database allowing us to add a record to a table without writing a single line of SQL.

// Create and populate an object.
$profile = new stdClass();
$profile->user_id = 1001;
$profile->profile_value='Inserting a record using insertObject()';
// Insert the object into the user profile table.
$result = JFactory::getDbo()->insertObject('#__user_profiles', $profile);

Notice here that we do not need to escape the table name; the insertObject method does this for us.

The insertObject method will throw a error if there is a problem inserting the record into the database table.

We need to ensure that the record does not exist before attempting to insert it, so adding some kind of record check before executing the insertObject method would be recommended.

Updating a Record

Using SQL

The JDatabaseQuery class also provides methods for building update queries, in particular update and set. We also reuse another method which we used when creating select statements, the where method.

$db = JFactory::getDbo();
$query = $db->getQuery(true);
// Fields to update.
$fields = array(
    $db->quoteName('profile_value') . ' = ' . $db->quote('Updating custom message for user 1001.'),
    $db->quoteName('ordering') . ' = 2'
// Conditions for which records should be updated.
$conditions = array(
    $db->quoteName('user_id') . ' = 42', 
    $db->quoteName('profile_key') . ' = ' . $db->quote('custom.message')
$result = $db->execute();

Using an Object

Like insertObject, the JDatabaseDriver class provides a convenience method for updating an object.

Below we will update our custom table with new values using an existing id primary key:

// Create an object for the record we are going to update.
$object = new stdClass();
// Must be a valid primary key value.
$object->id = 1;
$object->title = 'My Custom Record';
$object->description = 'A custom record being updated in the database.';
// Update their details in the users table using id as the primary key.
$result = JFactory::getDbo()->updateObject('#__custom_table', $object, 'id');

Just like insertObject, updateObject takes care of escaping table names for us.

The updateObject method will throw a error if there is a problem updating the record into the database table.

We need to ensure that the record already exists before attempting to update it, so we would probably add some kind of record check before executing the updateObject method.

Deleting a Record

Finally, there is also a delete method to remove records from the database.

$db = JFactory::getDbo();
$query = $db->getQuery(true);
// delete all custom keys for user 1001.
$conditions = array(
    $db->quoteName('user_id') . ' = 1001', 
    $db->quoteName('profile_key') . ' = ' . $db->quote('custom.%')
$result = $db->execute();

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