from Help:
For Paradox tables with primary indexes, the record is inserted into the dataset in a position based on its index.
For Paradox tables without primary indexes, the record is inserted into the dataset at the current position.
For dBASE, FoxPro, and Access tables, the record is physically appended to the dataset at the end. If an index happens to be active, the new record may appear in a position relative to the index, but the record is still actually stored at the end of the table.
For SQL databases, the physical location of the insert is implementation-specific. For indexed tables, the index is updated with the new record information.