At 07:32 PM 17/05/2006, you wrote:

>hello
>i have a very rudimentary knowledge of sql as it's only one part of
>the project im in right now and in order to find records in my
>database i have my delphi application generate sometimes very awkward
>queries and like for example
>
>select * from (select * from (select * from (select * from (select *
>from dicentries where id in (select id_dicentry from
>dskrptlink_dicentries where id_dskrpt = (select id from dskrpts where
>asdskrpt = 'ios'))) where id in (select id_dicentry from
>dskrptlink_dicentries where id_dskrpt = (select id from dskrpts where
>asdskrpt = 'iop'))) where id in (select id_dicentry from
>dskrptlink_dicentries where id_dskrpt = (select id from dskrpts where
>asdskrpt = 'ois'))) where id < 2067 order by id descending rows 20)
>order by id ascending
>
>(for some clarity: dskrptlink_dicentries.id_dicentry = foreign key on
>dicentries.id; dskrptlink_dicentries.id_dskrpt = foreign key on
>dskrpts.id => dskrptlink_dicentries is table establishing a
>many-to-many link between tables dicentries and dskrpts...so this
>query would ask for the last 20 of all those records in dicentries
>that are linked via dskrptlink_dicentries to ALL three records in
>dskrpts where dskrpts.asdskrpt = 'ois', asdskrpt = 'iop', asdskrpt =
>'ios' and then order them ascendingly)
>
>i'm pretty sure if i had better knowledge of sql there would be an
>easier way to express the same thing but my question is: is it worth
>it? will it make my searches faster or can i assume that firebird
>always looks for the fastest way possible?

Your question comes into the category "How long is a piece of
string?" If this query actually runs at all (doubtful) it will
probably take a week or two to complete.

Is it worth understanding the SQL language to use Firebird? Yes.
(understatement!!).

I think I might add your posting to my forthcoming book, "Essential
SQL for Skateboard Riders". :-)

Get your best SQL textbook and look up the keyword JOIN. If you
don't own an SQL textbook and you have a birthday coming soon, put it
at the top of your wish-list. If you attend an IT school, visit the library.

./heLen