SQL query to retrive data [closed] - mysql

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For these relations:
Customer(CID, Name, City, State),
Order(OID, CID, Date), and
Product(PID, ProductName, Price)
LineItem(LID, OID,PID, Number, TotalPrice),
where CID is a customer id and is a key for Customer, OID is an order id and is a key for Order, and LID is a line item id and is a key for LineItem. In addition the attribute CID of Order is a foreign key referring to the CID of Customer, that is, for each CID c of Order there is exactly one tuple of Customer whose CID attribute is c. The OID of LineItem is a foreign key referring to the OID of Order. There are several line items for the same order, a line item refers to a product and contains the quantity ordered for the product.
What is the query for:
List the products bought by all the customers of 'mycity'
#Edit
This is what I've tried so far:
Select ProductName
from Product
where PID in (
select PID
from LineItem
where OID in(
Select OID
from Order
where CID in(
select CID from customer where city='mycity'
)
)
);
This query however will return all the products bought by all customers from mycity. And the question requires only those products that everyone from 'mycity' have bought.
Not sure how to implement "All in" condition
#Edit2: Finally solved it :) Can someone please verify??

Answer 1

SELECT ProductName FROM Product
INNER JOIN LineItem ON LineItem.PID=Product.PID
INNER JOIN `Order` ON Order.OID=LineItem.OID
INNER JOIN Customer ON Order.CID=Customer.CID
WHERE Customer.City='mycity'
I think this should work

Answer 2

This query is solved in 2 parts: Create a view and query that view
Create view hview as (SELECT distinct count(distinct Customer.CID) as
uniquecustomer, count(distinct Customer.name), product.pid, product.Productname
FROM myorder
INNER JOIN Customer ON myorder.CID = Customer.CID
INNER JOIN LineItem ON myorder.OID = LineItem.oid
INNER JOIN Product ON Product.PID = LineItem.PID
where Customer.city = 'mycity'
group by Product.PID);
select productname from product where pid in(
select PID from hview where uniquecustomer in( SELECT count(distinct Customer.CID)
FROM myorder
INNER JOIN Customer ON myorder.CID = Customer.CID
INNER JOIN LineItem ON myorder.OID = LineItem.oid
INNER JOIN Product ON Product.PID = LineItem.PID
where Customer.city = 'mycity'));
Logic Used: create a view of items with distinct owners from mycity.
Query that view to find items that have distinct owners equal to number of distinct customers in mycity. Every item that has a distinct number of owners equal to the number of distinct customers of mycity are the products that are bought by everyone in mycity.
*myorder is the table name I used instead of order since thats a reserve word.

Answer 3

Better version in a single query:
select p1.productname from Product p1, myorder s1, lineitem l1, customer c1
where l1.pid=p1.pid
and l1.OID=s1.oid
and c1.cid=s1.cid
and c1.city='mycity'
group by p1.ProductName
having count(distinct c1.cid)=(select count(1) from customer c2 where c2.city='mycity');