Outer join and self-refer in Oracle - oracle

Question

I have customers with contract at various sites which must be charged.
There are two types of billing address for the sites: sites charged at the customer's address and sites charged to another address.
The kind of site is handled by the field 'status': if the site is charged at the customer's address, the field is equal to 'C'. If it is charged to a different site's address, it is equal to 'A' and the field 'bill_site_id' is filled with the 'site_id' used for billing. I want to retrieve, in one query, the address where I have to send the bill...
Let's say a customer have two sites (the A refers to the B for billing); the request obviously shows the two sites, but I only want the one used for billing (the B).
How to retrieve this one only?
Here is my query (anonymized, so please be gentle :-) )
SELECT CASE wp.status
WHEN 'A'
THEN wp2.name
ELSE c.NAME
END AS NAME,
CASE wp.status
WHEN 'A'
THEN wp2.adress
ELSE c.street
END AS street,
CASE wp.status
WHEN 'A'
THEN wp2.city
ELSE c.city
END AS city,
CASE wp.status
WHEN 'A'
THEN wp2.postcode
ELSE c.postcode
END AS postcode
FROM customer c, site wp, site wp2, customer_site cwp
WHERE c.idcompany = cwp.idcompany
AND cwp.site_id = wp.site_id
AND wp2.site_id(+) = wp.bill_site_id
AND c.idcompany = :someId
GROUP BY wp.status,
wp2.name,
wp2.adress,
wp2.city,
wp2.postcode

Answer 1

I am pretty sure I know what you want but am not 100% sure what 'ch.status' refers to in the query. Also i am not sure that from the information given you can achieve what you want ...
Hopefully the data structures are under your control so you can set it up how you want.
If I read your specification correctly then I think you want/need only 1 instance of the site table in the query, but it is then not clear how you identify the customer's address.
One way round this is for the site table to have an main_address flag. (I think this is the confusion around ch.status)
If there is a flag on the site table then ...
WHERE c.idcompany = cwp.idcompany
AND cwp.site_id = wp.site_id
AND (
(C.STATUS = 'C' AND WP.MAIN_ADDRESS = 1) OR
(C.STATUS = 'A' AND WP.SITE_ID = C.BILL_SITE_ID)
)
Another way would be to have the Main Adress and Billing addresses as foreign keys on the customer table, and to forget about the status flag so :
WHERE WP.SITE_ID = DECODE(C.BILLING_ADDRESS, NULL, C.MAIN_ADDRESS, C.BILLING_ADDRESS)
If this makes no sense then perhaps you can post a DESCRIBE of the tables involved.

Answer 2

Technically a Union is two queries, but you can run it in a single command and it should do what you want so I'm throwing it out as an option. :)
SELECT c.Name AS NAME, c.street AS STREET, c.city AS CITY, c.postcode AS postcode
FROM customer c
INNER JOIN customer_site cwp ON c.idcompany = cwp.idcompany
INNER JOIN site wp ON cwp.site_id = wp.site_id
WHERE c.idcompany = :someid AND wp.status = 'C'
UNION
SELECT wp2.name AS NAME, wp2.adress AS STREET, wp2.city AS CITY, wp2.postcode AS postcode
FROM customer c
INNER JOIN customer_site cwp ON c.idcompany = cwp.idcompany
INNER JOIN site wp ON cwp.site_id = wp.site_id
INNER JOIN site wp2 ON wp.bill_site_id = wp2.site_id
WHERE c.idcompany = :someid AND wp.status = 'A'
I can't see your table structure so it's probably possible to optimize more, but I think that'll help point you in a working direction. This may very well not be any faster then your existing query, but it's a fair bit easier to understand.