Hi,
Le jeu. 18 avr. 2019 à 22:41, David G. Johnston
<david.g.johnston@gmail.com> a écrit :
> Create a unique index over user_id, article_id on the test_article table.
> The system will never allow a duplicate to be inserted in the first place.
I know this and, indeed, I could have done it. But, the real thrust of
my question is how do I "drop out" of the query after finding the
first matching record. Putting indexes to the side - it's more of an
SQL question than just adding an index.
> That said your query is overly complicated...
> SELECT user_id, article_id
> FROM test_article
> GROUP BY user_id, article_id
> HAVING count(*) > 1
Sorry - the "WHERE 1 = (SELECT 1)" was just something I was testing
to get plans to be more complicated.
Forget that bit. Should have proofed better! :-(
> A where clause is optional and the composite and count in the select list aren't really needed
> unless you have some other unstated requirement for them.
What I want to know is as above - once I find one match - that's it,
all bets are off, there's no point in looking any further. A dupe
means that my previous attempt to insert UNIQUE records failed - I'd
like to be told of that sooner rather than later.
Thanks for your input!
Rgs,
Pól...
> David J.
