Original message from: Fabrice Scemama
>On finit par penser que ta question comporte en elle
>sa propre reponse :-)
>informe-toi sur les joins en particulier et le SQL en general.
>Tu critiqueras la liste et les gens ensuite.
>
>(translation to English-speaking mailing-list users:
> I replied 'RTFM' :-)
>
>Fabrice Scemama
>
>Dragos Stoichita wrote:
Let's get rid of those kind of messages. When you write a message
saying you are a beginner, there's always a little bunch of people like
you who particularly like to say: "go read the docs newbie" or
"go learn that" etc.
I am not someone who never reads the docs before asking a question.
I know SQL, I know joins, and all the people who told me to rewrite
the query would better have not answered my message, because
I already knew that.
I take your message as a personal insult, because I don't criticize
people without reason, and I did criticize this list because it was
justified.
I need help about only once every 2 or three months, because I am
able to use the docs and do my own work alone.
HERE I AM NOT ASKING HELP!
I asked a simple question: why the query with intersects is not only
slower, but with a factor of 10^something slower than the join one.
If the select returns a table of 1 column with n rows all integers,
sorting them ~n*logn, unique is ~n and intersect is ~n. I have here
a book on Algorithmics and have validated a course on this, I know
what I talk about. Why, with performant sorting, unique and intersect
algorithms, it takes 13 seconds???
I just want a real serious person that has knowledge to answer this
precise question, using an algorithmic demonstration. I only talk about
maths and algorithms here.
Please be serious in your answer next time.
Dragos Stoichita.