Re: Why is unique constraint needed for upsert?

On 7/23/2014 10:21 AM, Seamus Abshere wrote:
> hi all,
>
> Upsert is usually defined [1] in reference to a violating a unique key:
>
>> Insert, if unique constraint violation then update; or update, if not
>> found then insert.
>
> Is this theoretically preferable to just looking for a row that
> matches certain criteria, updating it if found or inserting otherwise?

what happens when two connections do this more or less concurrently, in
transactions?



--
john r pierce                                      37N 122W
somewhere on the middle of the left coast