how to join three tables on every time when model load

Question

I want to join three tables on every time when model load (for example on edit from page, on grid page in admin and detail page in front-end etc... ) in my custom module. can you please let me know where is best place to code for this (in model class, in resource class or collection class) and what function I should use for joining?

please help me to fix this.

Edited:

<?xml version="1.0"?>
<config>
    <modules>
        <Mynamespace_Mymodule>
            <version>1.0.4</version>
        </Mynamespace_Mymodule>
    </modules>
    <global>
        <resources>
            <mynamespace_mymodule_setup>
                <setup>
                    <module>Mynamespace_Mymodule</module>
                    <class>Mynamespace_Mymodule_Model_Resource_Setup</class>
                </setup>
            </mynamespace_mymodule_setup>
        </resources>
        <blocks>
            <mynamespace_mymodule>
                <class>Mynamespace_Mymodule_Block</class>
            </mynamespace_mymodule>
        </blocks>
        <helpers>
            <mynamespace_mymodule>
                <class>Mynamespace_Mymodule_Helper</class>
            </mynamespace_mymodule>
        </helpers>
        <models>
            <mynamespace_mymodule>
                <class>Mynamespace_Mymodule_Model</class>
                <resourceModel>mynamespace_mymodule_resource</resourceModel>
            </mynamespace_mymodule>
            <mynamespace_mymodule_resource>
                <class>Mynamespace_Mymodule_Model_Resource</class>
                <entities>
                    <table1>
                        <table>mynamespace_mymodule_table1</table>
                    </table1>
                    <table2>
                        <table>mynamespace_mymodule_table2</table>
                    </table2>                   
                    <table3>
                        <table>mynamespace_mymodule_table3</table>
                    </table3>                   
                </entities>
            </mynamespace_mymodule_resource>
        </models>
    </global>
    <adminhtml>
        <layout>
            <updates>
                <mynamespace_mymodule>
                    <file>mynamespace_mymodule.xml</file>
                </mynamespace_mymodule>
            </updates>
        </layout>
    </adminhtml>
    <admin>
        <routers>
            <adminhtml>
                <args>
                    <modules>
                        <Mynamespace_Mymodule before="Mage_Adminhtml">Mynamespace_Mymodule_Adminhtml</Mynamespace_Mymodule>
                    </modules>
                </args>
            </adminhtml>
        </routers>
    </admin>
</config>

Thanks in advance!

Answer 1

techguy4web,

In this case,you need make one table primary table and using join function[left join,Inner join] on Resource Model and Resource Model Collection class relation rest of two classes.

Add Tables into Model Collection :

You need to first work on collection class.Here,you need do add function _afterLoad() on collection class,w using this function you can mapping relation between there table.

On Resource Class : Mynamespace_Mymodule_Model_Resource_Mymodel_Collection

protected function _afterLoad()
{
$select= $this->getSelect();
$select->joinLeft(
    array('SecondTable'=>$this->getTable('yourmodel/secondtable')),
    'Maintable.key=SecondTable.key',
    array('*')
);

$select->joinLeft(
    array('3rdTable'=>$this->getTable('yourmodel/thirdatble')),
    'Maintable.key=3rdTable.key',
    array('*')
);
return parent::_afterLoad();
}

afterLoad() trigger a perform a operations after collection load.

Add Three tables into model

On resource class you need add multiple table using function _getLoadSelect() on Mynamespace_Mymodule_Model_Resource_Mymodel

 protected function _getLoadSelect($field, $value, $object)
    {
        $select = parent::_getLoadSelect($field, $value, $object);

        $select->join(
                array('SecondTable' => $this->getTable('yourmodel/secondtable')),
               'Maintable.key=SecondTable.key',
                array());

        $select->join(
                array('3rdTable' => $this->getTable('yourmodel/thirdatble')),
               'Maintable.key=3rdTable.key',
                array());

    return $select;
    }

If resource collection is not work then try this code at collection.php

Create two individual function.which is include rest of function to collection.

public function addSecondTable(){

$select= $this->getSelect();
$select->joinLeft(
        array('SecondTable'=>$this->getTable('yourmodel/SecondTable')),
        'Maintable.key=SecondTable.key',
        array('*')
    return $this;   
}

public function addThirdTable(){

    $this->getSelect()->joinLeft(
    array('3rdTable'=>$this->getTable('yourmodel/Thirdatble')),
    'Maintable.key=3rdTable.key',
    array('*'));
    return $this;   
}

You can use:

$collection = Mage::getResourceModel('mynamespace_mymodule/mymodule_collection');
$collection->addSecondTable()->addThirdTable();