I also tried it by taking the t1.t_id off of the selection list and it still worked.

You said it knows about the column from the one table but not the other table.

I guess I am a little confused here. I thought that the update would only know about the result set and not the underlying tables or tables the columns come from.

Is this not the case?

Because when I removed the ID and it know which record to update as well as the table it came from, I was a little confused.

Thanks,

Tom