$resource = Mage::getSingleton('core/resource');
$write = $resource->getConnection('core_write');
$read = $resource->getConnection('core_read');
$table = $resource->getTableName('your/model');

Tworzenie wpisów w DB:

$write->insert(
    $table,
    ['column_1' => 1, 'column_2' => 2]
);

Pobieranie z DB:

$select = $read->select()
    ->from(['tbl' => $table], ['entity_id', 'company'])
    ->join(['tbl2' => $table2], 'tbl.entity_id = tbl2.product_id', ['stuff'])
    ->where('name LIKE ?', "%{$name}%")
    ->group('company');
$results = $write->fetchAll($select);

Update DB:

$write->update(
    $table,
    ['column_1' => 3, 'column_2' => 4],
    ['entity_id = ?' => 123]
);

Usuwanie z DB:

$write->delete(
    $table,
    ['entity_id IN (?)' => [123, 456]]
);

Wstawianie wielu:

$rows = [
    ['col_1'=>'value1', 'col_2'=>'value2', 'col_3'=>'value3'],
    ['col_1'=>'value3', 'col_2'=>'value4', 'col_3'=>'value5'],
];
$write->insertMultiple($table, $rows);

Insert Update On Duplicate:

$data = [];
$data[] = [
    'sku' => $sku,
    'name' => $name
];
$write->insertOnDuplicate(
    $table,
    $data, // może też być array of $rows jak we Wstawianie wielu
    ['name'] // to jest pole, które będzie uaktualnione w wypadku duplikatu
);