I have a list of prices for a stocks on each day in a table. I want to make a table that can override the price for a stock on a particular day. If XYZ is $1 on 1/1/2007 according to my main price table, I might want to substitute in $2 for that day instead in my override table. Then, I'd like to union the two, with the $2 record showing as the price for that day.