function sql_index_drop($dbms, $index_name, $table_name)
{
	global $dbms_type_map, $db;
	global $errored, $error_ary;

	switch ($dbms)
	{
		case 'mssql':
			$sql = 'DROP INDEX ' . $table_name . '\.' . $index_name . ' ON ' . $table_name;
			_sql($sql, $errored, $error_ary);
		break;

		case 'mysql_40':
		case 'mysql_41':
			$sql = 'DROP INDEX ' . $index_name . ' ON ' . $table_name;
			_sql($sql, $errored, $error_ary);
		break;

		case 'firebird':
		case 'oracle':
		case 'postgres':
		case 'sqlite':
			$sql = 'DROP INDEX ' . $table_name . '_' . $index_name;
			_sql($sql, $errored, $error_ary);
		break;
	}
}

function sql_create_primary_key($dbms, $table_name, $column)
{
	global $dbms_type_map, $db;
	global $errored, $error_ary;

	switch ($dbms)
	{
		case 'firebird':
		case 'postgres':
			$sql = 'ALTER TABLE ' . $table_name . ' ADD PRIMARY KEY (' . implode(', ', $column) . ')';
			_sql($sql, $errored, $error_ary);
		break;

		case 'mssql':
			$sql = "ALTER TABLE [{$table_name}] WITH NOCHECK ADD ";
			$sql .= "CONSTRAINT [PK_{$table_name}] PRIMARY KEY  CLUSTERED (";
			$sql .= '[' . implode("],\n\t\t[", $column) . ']';
			$sql .= ') ON [PRIMARY]';
			_sql($sql, $errored, $error_ary);
		break;

		case 'mysql_40':
		case 'mysql_41':
			$sql = 'ALTER TABLE ' . $table_name . ' ADD PRIMARY KEY (' . implode(', ', $column) . ')';
			_sql($sql, $errored, $error_ary);
		break;

		case 'oracle':
			$sql = 'ALTER TABLE ' . $table_name . 'add CONSTRAINT pk_' . $table_name . ' PRIMARY KEY (' . implode(', ', $column) . ')';
			_sql($sql, $errored, $error_ary);
		break;

		case 'sqlite':
			$sql = "SELECT sql
				FROM sqlite_master 
				WHERE type = 'table' 
					AND name = '{$table_name}'
				ORDER BY type DESC, name;";
			$result = _sql($sql, $errored, $error_ary);

			if (!$result)
			{
				break;
			}

			$row = $db->sql_fetchrow($result);
			$db->sql_freeresult($result);

			$db->sql_transaction('begin');

			// Create a backup table and populate it, destroy the existing one
			$db->sql_query(preg_replace('#CREATE\s+TABLE\s+"?' . $table_name . '"?#i', 'CREATE TEMPORARY TABLE ' . $table_name . '_temp', $row['sql']));
			$db->sql_query('INSERT INTO ' . $table_name . '_temp SELECT * FROM ' . $table_name);
			$db->sql_query('DROP TABLE ' . $table_name);

			preg_match('#\((.*)\)#s', $row['sql'], $matches);

			$new_table_cols = trim($matches[1]);
			$old_table_cols = preg_split('/,(?=[\\sa-z])/im', $new_table_cols);
			$column_list = array();

			foreach ($old_table_cols as $declaration)
			{
				$entities = preg_split('#\s+#', trim($declaration));
				if ($entities == 'PRIMARY')
				{
					continue;
				}
				$column_list[] = $entities[0];
			}

			$columns = implode(',', $column_list);

			// create a new table and fill it up. destroy the temp one
			$db->sql_query('CREATE TABLE ' . $table_name . ' (' . $new_table_cols . ', PRIMARY KEY (' . implode(', ', $column) . '));');
			$db->sql_query('INSERT INTO ' . $table_name . ' (' . $columns . ') SELECT ' . $columns . ' FROM ' . $table_name . '_temp;');
			$db->sql_query('DROP TABLE ' . $table_name . '_temp');

			$db->sql_transaction('commit');
		break;
	}
}