Can anyone please help me figure this out, I have 3 tables: Customer, Products and Products_ordered and I am trying to find customers who have ordered more than 1 product. Here is my query:
SELECT customer_id, product_id
FROM product_ordered
GROUP BY customer_id
HAVING COUNT (customer_id)>1;
I am getting this error: Error report: SQL Error: ORA-00979: not a GROUP BY expression 00979. 00000 - "not a GROUP BY expression"
Thanks for helping