Magento 2 Programming : Get default core write and read resource (row direct sql)

Magento 2 have concept of resource yes for interact wih database , this tutorial  cover the technique of how getting the  global resource and using for  play with any SQL query and execute directly …

A – Fist you need inject the object resource  Magento\Framework\App\Resource inside di.xml here I will inject to my custom action of controller MassDelete ...

 
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">  
    <type name="Ibnab\DeleteOrders\Controller\Adminhtml\Order\MassDelete">
        <arguments>
            <argument name="deleteorderAction" xsi:type="array">
                <item name="context" xsi:type="string">Magento\Backend\App\Action\Context</item>
                <item name="resource" xsi:type="string">Magento\Framework\App\ResourceConnection</item>
            </argument>
        </arguments>
    </type>
</config>
 

B - inside of My action  I get the resource and I put to class variable ;

 
  protected  _resource;
  public function __construct(Context $context,
\Magento\Framework\App\ResourceConnection $resource)
  {
    $this->_resource = $resource;
    parent::__construct($context);
 
  }
 

 
$connection = $this->_resource->getConnection(\Magento\Framework\App\ResourceConnection::DEFAULT_CONNECTION);
        $showTables =$connection->fetchCol('show tables');
 

D – Some example :

get the name of table it concat the prefix

 
$tblSalesOrder = $connection->getTableName('sales_order');
 

 
$result1 = $connection->fetchAll('SELECT quote_id FROM `'.$tblSalesOrder.'` WHERE entity_id='.$orderId);
 

or custom query you can raw query with :

 
$connection->rawQuery('DELETE FROM `'.$tblSalesCreditmemoGrid.'` WHERE order_id='.$orderId);