On Fri, May 26, 2023 at 8:02 PM jian he <jian.universal...@gmail.com> wrote:

>
> I still feel confused about "the key values".
>

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.

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