Adding an array in a SQL query

[ZiNgA BuRgA]

What are you trying to pull exactly?
From the query, it seems like you're pulling the latest threads which have at least one of the specified xtattachments attached to the thread.
If it's a list of fields, you're probably going to need the user to enter what fields they're using at some place.

As for the above post, are you trying to filter by type?  You shouldn't trust the MIME type as this is sent by the user and XThreads doesn't do any validation on it (it just stores it in case there may be a use in the future).  Checking file extensions is probably more reliable.