/**
* Compiles an array of ORDER BY statements into an SQL partial.
*
* @param object $db Alt_Database instance
* @param array $columns sorting columns
* @return string
*/
protected function _compile_order_by(Alt_Database $db, array $columns)
{
$sort = array();
foreach ($columns as $group) {
list($column, $direction) = $group;
if (is_array($column)) {
// Use the column alias
$column = $db->quote_identifier(end($column));
} else {
// Apply proper quoting to the column
$column = $db->quote_column($column);
}
if ($direction) {
// Make the direction uppercase
$direction = ' ' . strtoupper($direction);
}
$sort[] = $column . $direction;
}
return 'ORDER BY ' . implode(', ', $sort);
}
