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Difference between revisions of "Inserting, Updating and Removing data using JDatabase"

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{{dablink|'''Version Note:''' While this document pertains to Joomla! 2.5 and 3.x, $db->execute() does not exist in Joomla 2.5. In that case, change $db->execute() to $db->query(). Using $db->query() is possible in Joomla 3.x but will generate a deprecated notice.}}
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This tutorial is split into two independent parts:
 
This tutorial is split into two independent parts:
 
* Inserting, updating and removing data from the database. It also touches on transactions
 
* Inserting, updating and removing data from the database. It also touches on transactions

Revision as of 15:28, 1 September 2013

This tutorial is split into two independent parts:

  • Inserting, updating and removing data from the database. It also touches on transactions
  • Selecting data from a table and retrieving it in a variety of different forms

This section of the documentation looks at inserting, updating and removing data from a database table. To see the other part click here

Contents

Introduction

Joomla provides a sophisticated database abstraction layer to simplify the usage for third party developers. New versions of the Joomla Platform API provide additional functionality which extends the database layer further, and includes features such as connectors to a greater variety of database servers and the query chaining to improve readability of connection code and simplify SQL coding.

Joomla can use different kinds of SQL database systems and run in a variety of environments with different table-prefixes. In addition to these functions, the class automatically creates the database connection. Besides instantiating the object you need just two lines of code to get a result from the database in a variety of formats. Using the Joomla database layer ensures a maximum of compatibility and flexibility for your extension.

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.
$query
    ->insert($db->quoteName('#__user_profiles'))
    ->columns($db->quoteName($columns))
    ->values(implode(',', $values));
 
// Set the query using our newly populated query object and execute it.
$db->setQuery($query);
$db->execute()

Using an Object

The JDatabaseDriver also class provides us with a convenience 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_key='custom.message';
$profile->profile_value='Inserting a record using insertObject()';
$profile->ordering=1;
 
// 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(
    'profile_value=\'Updating custom message for user 1001.\'',
    'ordering=2');
 
// Conditions for which records should be updated.
$conditions = array(
    'user_id=42', 
    'profile_key=\'custom.message\'');
 
$query->update($db->quoteName('#__user_profiles'))->set($fields)->where($conditions);
 
$db->setQuery($query);
 
$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 inserting 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

Just as there are select, insert and update method calls, there is also a delete method for remove records from the database.

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

Transactions

Joomla Joomla 3.x introduced SQL transactions (where supported) via the JDatabaseDriver's transactionStart, transactionCommit and transactionRollback. This supersedes the queryBatch method which was introduced in Joomla Joomla 2.5.

$db = JFactory::getDbo();
 
try
{
    $db->transactionStart();
 
    $query = $db->getQuery(true);
 
    $values = array($db->quote('TEST_CONSTANT'), $db->quote('Custom'), $db->quote('/path/to/translation.ini'));
 
    $query->insert($db->quoteName('#__overrider'));
    $query->columns($db->quoteName(array('constant', 'string', 'file')));
    $query->values(implode(',',$values));
 
    $db->setQuery($query);
    $result = $db->execute();
 
    $db->transactionCommit();
}
catch (Exception $e)
{
    // catch any database errors.
    $db->transactionRollback();
    JErrorPage::render($e);
}

Anything between the transactionStart and transactionCommit methods are not executed until transactionCommit is called. If an exception occurs, we can roll back the changes using the transactionRollback method. This allows us to return the database to the original state if a problem occurs even though we may execute a number of changes to the database's tables.