Why are you re-posting your original post? As I said in my last post it makes absolutely zero difference which column or table is on which side of an equality check. You even noted that the execution plans are identical, that is because there is no logical difference in the first two.

If you really want some help you should read the articles Gail suggested. Then come back and post some details instead of a vague query. Remember that indexing and performance have a LOT to do with how the table is defined. It is more than just a couple of column names thrown into a query. To help we would need to see the table structures and the indexes at the very least.