oracle sql developer查询3个表

Question

in oracle sql i have this 3 tables with names and columns: 1.orders:
customerid orderid (primary key)

2.orderlines: orderlineid (primary key) orderid productid

3.products: prodid (primary key) category

and i want to find the customers(customerid) that have make at least 1 order which contains products from at least 3 different categories.if someone can help me with this query.thanks a lot!

tried a lot of things but nothing worked since i am a newbie in SQL here is an example,since i dont know what i am really doing dont give it to much attention.thank again.

select customerid,count(orderid) as total
from (select customerid,orderid,prodid,distinct category
from orders o,orderlines n,products p
where o.orderid=n.orderid and n.prodid=p.prodid )
group by (customerid);

Answer 1

SELECT DISTINCT customerid 
FROM ORDERS O
INNER JOIN PRODUCTS P
ON (P.prodid = O.prodid)
INNER JOIN ORDERLINES OL
ON (O.prodid = OL.prodid AND O.orderid = P.orderid)
GROUP BY O.customerid,O.orderid
HAVING
COUNT(DISTINCT p.category) >= 3

In Your Style of JOINS (My Favourite too)

SELECT DISTINCT customerid 
FROM ORDERS O,PRODUCTS P,ORDERLINES OL
WHERE (O.prodid = P.prodid)
AND (O.prodid = OL.prodid AND O.orderid = P.orderid)
GROUP BY O.customerid,O.orderid
HAVING COUNT(DISTINCT p.category) >= 3