protected function _getValue( $sql, $column, $name = 'db' )
	{
		$result = $this->_getConnection( $name )->create( $sql )->execute();

		if( ( $row = $result->fetch() ) === false ) {
			throw new MW_Setup_Exception( sprintf( 'No rows found: %1$s', $sql ) );
		}

		if( array_key_exists( $column, $row ) === false ) {
			throw new MW_Setup_Exception( sprintf( 'No column "%1$s" found: %2$s', $column, $sql ) );
		}

		$result->finish();

		return $row[$column];
	}