multiple tables for Zend Framework 2

Question

I'm new to Zend Framework 2. I successfully completed the Album tutorial for ZF2. Now I'd like to display only a certain data from multiple tables in the database. I have a simple database setup with tables, for example, person, books, status..etc. It's really not important what the database's supposed to do. What I would like to know is if there's a tutorial that would show me step-by-step guidance to display data from table joins. I have seen snippets of codes showing how to do joins, but I haven't found any tutorials on setting up the classes, and how to configure Module.php. In other words, the Module in Album has one table name hardcoded in getServiceConfig(). But how do I set it up so it knows I'm requesting data from multiple tables. Also, if I want to setup the relationship, do I still create class for database tables like in Album tutorial, or is it going to be something different. Can you please help, or show me the right path? If you know of any tutorial that explains handling multiple tables, that would be great.

Answer 1

Just to expand on Robs excellent answer, its simple to take it a step further and populate multiple objects to form the relationship you require.

<?php

// Given that $dbAdapter is an instance of Zend\Db\Adapter\Adapter

use Zend\Db\Sql\Select();
use Zend\Db\ResultSet\ResultSet();

$select = new Select();
$select->from('album')
   ->columns(array('album.*', 'artist.*'))
   ->join('artist', 'album.artist_id' = 'artist.artist_id');

$statement = $dbAdapter->createStatement();
$select->prepareStatement($dbAdapter, $statement);
$driverResult = $statement->execute(); // execute statement to get result

$resultset = new ResultSet();
$resultset->setDataSource($driverResult);

$albumHydrator = new AlbumHydrator;
$artistHydrator = new ArtistHydrator;

foreach($resultset as $row) { // $row is an ArrayObject
    $album = $albumHydrator->hydrate($row);
    $artist = $artistHydrator->hydrate($row);
    $album->setArtist($artist);
}

You should also look at hydrating result sets to build your objects for you directly from the ResultSet:

http://framework.zend.com/manual/2.0/en/modules/zend.db.result-set.html

Answer 2

The ablums tutorial uses Zend\Db\TableGateway which does not support joining to multiple tables.

You need to use Zend\Db directly or via a mapper class, such as AbstractDbMapper within the ZfcBase module.

The basic usage looks like this:

<?php

// Given that $dbAdapter is an instance of Zend\Db\Adapter\Adapter

use Zend\Db\Sql\Select();
use Zend\Db\ResultSet\ResultSet();

$select = new Select();
$select->from('album')
   ->columns(array('album.*', 'a_name' => 'artist.name'))
   ->join('artist', 'album.artist_id' = 'artist.id');

$statement = $dbAdapter->createStatement();
$select->prepareStatement($dbAdapter, $statement);
$driverResult = $statment->execute();

$resultset = new ResultSet();
$resultset->initialize($driverResult); // can use setDataSource() for older ZF2 versions.

foreach ($resultset as $row) {
        // $row is an ArrayObject
}

The join() method is used to perform the join between the album and artist table. We also use columns() to select which columns are returned. In this case, I create an alias called a_name for the name column within the artist table.

Once the Select object is set up, then the rest is the standard Db code that will return a ResultSet object for you containing the data.

Answer 3

use Zend\Db\Sql\Select;
$select = new Select();
// or, to produce a $select bound to a specific table
// $select = new Select('foo');

$select->join(
     'foo' // table name,
     'id = bar.id', // expression to join on (will be quoted by platform object before insertion),
     array('bar', 'baz'), // (optional) list of columns, same requiremetns as columns() above
     $select::JOIN_OUTER // (optional), one of inner, outer, left, right also represtned by constants in the API
);

$select->from(array('f' => 'foo'))  // base table
    ->join(array('b' => 'bar'),     // join table with alias
    'f.foo_id = b.foo_id');         // join expression