From time to time I have to deal with my least favorite subjects like DB2. While DB2 has a functional SQL, it’s dated and has not really kept up with SQL language improvements over the years. But it is all that I have to flow data from the IBM AS400 to the outside world (** it could be worst… like dealing with old COBOL programs). So  lets talk about updating column values that involve more that one table. Yeah, joined tables that have to have one or more columns updated.  Why would one need to do this? From time to time one needs to collect batches of rows from more…