only firebird supports limit.

@var array

only supports ‘table’ and ‘flags’ if <var>$result</var>

is a table name.

@param object|string $result DB_result object from a query or a string containing the name of a table.  While this also accepts a query result resource identifier, this behavior is deprecated.  @param int $mode a valid tableInfo mode

@return array an associative array with the information requested.  A DB_Error object on failure.

@see DB_common::tableInfo()