[Freddie Bingham]

Thread titles are not indexed so the query to grab a certain letter are going to grind on a large forum. You could index thread titles to help but that would be an index on a long varchar field so it might affect your performance.

The best solution would be to add a field that contains the first letter only, a 1 char field or an integer field (1 through 26) and place an index on that. Then you set that field when the thread is posted or when the title is changed. Then when someone clicks on A you could do a query on the new field to see what threadids match.