Re: Help to simplify sample query

Dnia 2004-03-09 06:41, Użytkownik Daniel Henrique Alves Lima napisał:
> Hi guys, i have a new question about how to simplify a query. I have
> the tables area_course(cd_area,cd_course) and
> teacher_course(cd_teacher,cd_course) and a set of pairs of values
> {(1,2),(98,45),(11,0),...}.
>
> Now, i must to select the areas which courses appears in
> teacher_course and match with the set of pairs. Something like :
>
> select cd_area from area a1 where
> exists (select * from teacher_course c2 where c2.cd_course =
> a1.cd_course and c2.cd_teacher = 1 and c2.cd_course = 2) and
> exists (select * from teacher_course c2 where c2.cd_course =
> a1.cd_course and c2.cd_teacher = 98 and c2.cd_course = 45) and
> exists (select * from teacher_course c2 where c2.cd_course =
> a1.cd_course and c2.cd_teacher = 11 and c2.cd_course = 0) and
> ....
>
> This is just a sample. The whole query is giant and its use other
> tables/columns. Is there a best way to write this query ?

Can you try this query ? :

select cd_area from area a1
join teacher_course c2 using (cd_course)
where (cd_teacher,cd_course) in (select 1,2 union select 98,45 union
select 11,0);

Regards,
Tomasz Myrta