I encountered a problem with Oracle's MERGE DML yesterday. What I was trying to do is use the "Upsert" feature of the merge, except with no distinct source. All of the searching I did for the MERGE showed examples of how to merge data from a source into a target. In my case, I thought the source and the target were the same. This is what I initially tried. It didn't work. It turns out that if the source (s) returns an empty set, then the merge is effectively a no-op 1: merge into MY_TARGET t 2: using ......