There is no real concept of "first" and "last" in a table, the preciuse defintion being that a table is an "unordered set of rows". Therefore it could theoretically be any value from the second table that gets used.

You will find many people suggesting the "update from" syntax should be deprecated by Microisoft and preferably not used, as it does not make it obvious what will happen in this situation. It is certainly non-ansi standard, but if used carefully has some good uses. The critical thing to be aware of with it is to ensure that exactoly ONE row will be matched for the update, otherwise the effects are effectively undetermined.

You need to find a way of ensuring exactky one row gets matched, maybe have a look at thge merge statement.

Mike