This post is use for run sql query without using model in magento2. bY using this code we can get result execute query for create, read, update and delete.

// object manager Instance
$object_Manager = \Magento\Framework\App\ObjectManager::getInstance(); 
$get_resource   = $object_Manager->get('Magento\Framework\App\ResourceConnection');
$connection     = $get_resource->getConnection(); // get connection

// gives table name with prefix
$your_table_name = $get_resource->getTableName('employee'); // add your table Name

// Select Data from table in Magento2
$select_sql = "Select * FROM " . $your_table_name;
$result_query = $db_connection->fetchAll($select_sql); 
foreach( $result_query as $key => $values )
{
	// and table fields as key in array.
	echo "key as fields => ".$key." \n ";
    // it will gives associated array
    echo "values of Query => ".$values." \n ";
}

Magento2 : Custom Select Query

// Select Data from table in Magento2
$select_sql = "Select * FROM " . $your_table_name;
$result_query = $db_connection->fetchAll($select_sql); 
foreach( $result_query as $key => $values )
{
    // and table fields as key in array.
    echo "key as fields => ".$key." \n ";
    // it will gives associated array
    echo "values of Query => ".$values." \n ";
}

Magento2 : Custom Delete Query

// Delete Data from table in Magento2
$delete_sql = "Delete FROM " . $your_table_name." Where user_id = 116";
$db_connection->query($delete_sql);

Magento2 : Custom Insert Query

 
// Insert Data into table in Magento2
$insert_sql = "Insert Into " . $your_table_name . " (user_id,ser_name, ser_code, ser_salary) Values ('','TeSt','TeSt20','99999')";
$db_connection->query($insert_sql);

Magento2 : Custom Update Query

// Update Data into table in Magento2
$update_sql = "Update " . $your_table_name . "Set user_salary = 989898 where euser_id = 116";
$db_connection->query($update_sql);

Magento2 : All SQl Query


// object manager Instance
$object_Manager = \Magento\Framework\App\ObjectManager::getInstance(); 
$get_resource   = $object_Manager->get('Magento\Framework\App\ResourceConnection');
$connection     = $get_resource->getConnection(); // get connection

// gives table name with prefix
$your_table_name = $get_resource->getTableName('employee'); 
// add your table Name

// Select Data from table in Magento 2
$select_sql = "Select * FROM " . $your_table_name;
$result_query = $db_connection->fetchAll($select_sql); 

foreach( $result_query as $key => $values )
{
    // and table fields as key in array.
    echo "key as fields => ".$key." \n ";
    // it will gives associated array
    echo "values of Query => ".$values." \n ";
}

// Delete Data from table in Magento 2
$delete_sql = "Delete FROM " . $your_table_name." Where user_id = 116";
$db_connection->query($delete_sql);
 
// Insert Data into table in Magento 2
$insert_sql = "Insert Into " . $your_table_name . " (user_id,ser_name, ser_code, ser_salary) Values ('','TeSt','TeSt20','99999')";
$db_connection->query($insert_sql);

// Update Data into table in Magento 2
$update_sql = "Update " . $your_table_name . "Set user_salary = 989898 where euser_id = 116";
$db_connection->query($update_sql);