Обсуждение: SQL Query
Dear all,
I want to do a query to my PostgreSQL database. I want to use it in a PHP web client that I have got, but also
I have tried in the back-end.
I have the following tables on my database ( I translate the field names from Spanish into English)
cdroms
-------
code_cdroms
items
-----
code_items
description
cdroms_items
-------------
code_cdroms
code_items
loans
----------
code_loan
reservations
--------
code_reservation
The Query I want to execute is to search the cdroms that contains an item with the description provided by a form by the user.
That query works fine, it is just a simple join among cdroms, items and cdroms_items.
My problem shows up when I want to create two new fields to show whether the cdrom is on loan or is booked (someone made a reservation).
After reading some books and web sites, I concluded to use the CASE statement ( I do not know if there is any other alternative). I tried it, and it
worked, but only in the case there is any register in the loans or reservations tables, if there is not, the back-end says that you are trying to get more
than 200 registers. What am I doing wrong? Here you have the SQL query. I translated the name of the fields, hope there is no mistake.
I search for a string 'net' in the description field of the items table:
SELECT
cdroms.code_cdroms,cdroms_etiqueta,items.description,loans.code_loans,
loans.tabletype,reservations.code_reservations,reservations.tabletype,
(case
when
cdroms.code_cdroms=cdroms_items.code_cdroms
and cdroms.code_cdroms=code_prestamo
and cdroms_items.code_items=items.code_items
and items.description like %net%
then 'Yes' else 'No'
end)
as onloan,
(case
when
cdroms.code_cdroms=cdroms_items.code_cdroms
and cdroms.code_cdroms=code_loans
and cdroms.code_cdroms= ANY (select code_reservations from
reservations)
and cdroms_items.code_items=items.code_items
and items.description like %net%
then 'Yes' else 'No'
end)
as booked
from cdroms,items,cdroms_items,loans,reservations
where
cdroms.code_cdroms=cdroms_items.code_cdroms
and loans.tabletype='cdroms'
and cdroms_items.code_items=items.code_items
and items.description like '%net%'; Sorry for my English. Hope you can understand. Is is a problem of concept or a sintax problem? Many thanks in advance Regards Miguel
Sorry If i didnt make clear which are the fields and which are the tables. The tables are the ones "underlined", so I have cdroms, items, cdroms_items, loans and reservations. I just left the important fields in order not to confuse the people, and just wrote the name of the fields that are the primary keys and also the foreign keys. An item can be in different cdroms, and a cdrom can have different items, thats why i have the table cdroms_items for the n to n relation. I forgot to put the name of some fields when I translated into English, I am sorry about it. In the tables loans and reservations i added a field called typetable, a string where i store wich kind of object is loaned or booked, this is because I also have a hardware table, where i store names of different hardware that also could be loaned or booked. The idea is that the loanable and bookable objets and therefore the number of tables will be increased (books,magazines, etc). I reviewed the query and i noticed that I didnt translate well some names, sorry again. Hope that now you can help me out, i am getting close to the dateline. Many thanks Miguel ---------------- Reviewed information ---------------------------- In loans i cdroms ------- code_cdroms label items ----- code_items description cdroms_items ------------- code_cdroms code_items loans ---------- code_loan typetable reservations -------- code_reservation typetable SELECT cdroms.code_cdroms,cdroms_label,items.description,loans.code_loans, loans.tabletype,reservations.code_reservations,reservations.tabletype, (case when cdroms.code_cdroms=cdroms_items.code_cdroms and cdroms.code_cdroms=code_loan and cdroms_items.code_items=items.code_items and items.description like %net% then 'Yes' else 'No' end) as onloan, (case when cdroms.code_cdroms=cdroms_items.code_cdroms and cdroms.code_cdroms=code_loan and cdroms.code_cdroms= ANY (select code_reservations from reservations) and cdroms_items.code_items=items.code_items and items.description like %net% then 'Yes' else 'No' end) as booked from cdroms,items,cdroms_items,loans,reservations where cdroms.code_cdroms=cdroms_items.code_cdroms and loans.tabletype='cdroms' and cdroms_items.code_items=items.code_items and items.description like '%net%'; ----- Original Message ----- From: "Adam Lang" <aalang@rutgersinsurance.com> Cc: "PostgreSQL PHP" <pgsql-php@postgresql.org> Sent: Tuesday, September 11, 2001 2:52 PM Subject: Re: [PHP] SQL Query > If you could give the table layouts a little bit better, I may be able to > help. I can't quite tell what the table names are and what the fields are. > > As a preliminary guess, it almost looks like you don't have fields in the > other tables to properly link thedata... but again I can't tell for sure. > > Adam Lang > Systems Engineer > Rutgers Casualty Insurance Company > http://www.rutgersinsurance.com > ----- Original Message ----- > From: "Miguel González" <iafmgc@unileon.es> > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) >