need help with tricky mySQL query - mysql

Question

I'm asking for an awful lot here - but maybe some SQL guru can show me how to extract the data I want and save me 10+ hours of google-time(tm)?
These are my tables, with only relevant fields displayed:
**event**
id
cust_id
....
.
**art**
id
art_name
...
.
**event_art**
event_id
art_id
...
.
**price**
cust_id
art_id
price
...
Prices in the "price" DB with user ID "0" is standard price, if an entry exists with art_id and cust_id that is customer specific price for that article.
What I have is cust_id and what I have for output now is just the customer specific prices with SQL:
SELECT * FROM price WHERE cust_id='{$custID}'
But I'd like to include prices for previously ordered articles, even if they do not have a customer specific price.
So what I need is to:
1 Get all id's from table event where cust_id = custID
2 Get all distinct article ID's on those orders from table event_art
3 Output "id" and "art_name" of article from "art" and "price" from price table using custID or 0 for standard price if no entry exists.
To me this sounds like a multi-line JOIN that's a bit outside my scope of SQL knowledge. Could somebody help me out, point me to a guide that deals with similar issues or... well, something?
Thanks in advance!

Answer 1

SELECT art_id, price
FROM price
WHERE cust_id = $cust_id
UNION ALL
SELECT art_id, price
FROM (
SELECT DISTINCT art_id
FROM event e
JOIN event_art ea
ON ea.event_id = e.id
WHERE e.cust_id = $cust_id
AND ea.art_id NOT IN
(
SELECT art_id
FROM price
WHERE cust_id = $cust_id
)
) e
JOIN price p
ON p.cust_id = 0
AND p.art_id = e.art_id
Make sure that (cust_id, art_id) (in this order) is a PRIMARY KEY or a UNIQUE INDEX on price.

Answer 2

Had to make some small changes to indicate which table was used where in the SQL, but pretty much copy&paste so not bad at all :P
SELECT price.art_id, price.price
FROM price
WHERE cust_id =114
UNION ALL
SELECT e.art_id, p.price
FROM (
SELECT DISTINCT art_id
FROM event e
JOIN event_art ea ON ea.event_id = e.id
WHERE e.cust_id =114
AND ea.art_id NOT
IN (
SELECT price.art_id
FROM price
WHERE cust_id =114
)
)e
JOIN price p ON p.cust_id =0
AND p.art_id = e.art_id

Answer 3

SELECT DISTINCT
a.id,
a.art_name,
COALESCE(p.price, p0.price) AS price
FROM event e
INNER JOIN event_art ea ON e.id = ea.event_id
INNER JOIN art a ON ea
LEFT JOIN price p ON p.art_id = a.id AND p.cust_id = e.cust_id
LEFT JOIN price p ON p.art_id = a.id AND p.cust_id = 0