Re: explicit-locking.html "key values" reference

The "key" here is the Foreign Key relationship.  In short, FOR NO KEY UPDATE, promises that PK/FK values on the table will not be changed.  Only non-FK/PK columns can be changed.  In neither case may the row be removed either since that would necessitate changing the key to "non-existent".  However, the "UPDATE" part basically means "I am going to update some other column".  On the KEY SHARE side you basically get "I only care that this row/relationship continues to exist, you may change other attributes".

David J.