[Bryce]

I would advise against creating a table within the MySQL database used for XCart, as I have noticed that the tables I'd created on my own have been deleted during the last two minor updates of XCart modules (and basic updates of the XCart platform itself).

Instead, I recommend creating a new database just for your new table, and have the database user have read/write permissions, just like it would have for the XCart database.

For queries that involve both databases, just add the database name prior to the table name, such as...

SELECT * FROM `xcart_database`.`xcart_table`, `custom_database`.`custom_table` WHERE `xcart_database`.`xcart_table`.`unique_id` = `custom_database`.`custom_table`.`xcart_unique_id`