SQL(inner join with select statement)

Question

I have 2 tables auction and customer

auction

custId|itemName|yearsUsed|bidPrice
   1  | MacBook|    2    |  1500
   3  |  Dell  |    1    |  1000
   2  | MacBook|    2    |  1500

customer

 custId|custName
   1   | tom
   2   | jerry
   3   | susan

I want to query for those customers name, the item name and the bidding price for who have bided the same price for an item and the years used by the owner as well

The following query returns the item name which has the same bidding price by the customers

  SELECT ac.itemName,
         ac.yearsUsed,
         ac.bidPrice 
    FROM auction ac 
GROUP BY ac.itemName,
         ac.yearsUsed,
         ac.bidPrice 
  HAVING COUNT(*) > 1;

output

itemName yearsUsed  bidPrice
----------------------------
 MacBook     2       1500

Now I want to query for the customer name who had bid the same price for the item

  SELECT ac.itemName,
         ac.yearsUsed,
         ac.bidPrice 
    FROM auction ac 
         INNER JOIN (
                     SELECT custName 
                       FROM customer
                    ) c 
               ON c.custId = ac.custId 
GROUP BY ac.itemName,
         ac.yearsUsed,
         ac.bidPrice 
  HAVING COUNT(*) > 1;

I get an error

ERROR at line 1:
ORA_00904:"C"."CUSTID": invalid identifier

I am using sqlplus

Answer 1

You must add custid in the inner query.

SELECT 
  ac.itemName,
  ac.yearsUsed,
  ac.bidPrice 
FROM 
 auction ac INNER JOIN
    (SELECT custName,
      -- The following CUSTID was missing:
     CUSTID 
     FROM customer) c ON c.custId = ac.custId 
GROUP BY ac.itemName,ac.yearsUsed,ac.bidPrice 
HAVING COUNT(*) > 1;

However , in your case, the subquery is not necessary.

SELECT 
  ac.itemName,
  ac.yearsUsed,
  ac.bidPrice 
FROM 
 auction ac INNER JOIN
 customer c ON c.custId = ac.custId 
GROUP BY 
   ac.itemName,
   ac.yearsUsed,
   ac.bidPrice 
HAVING COUNT(*) > 1;

If you also need, as per your comment, the customers' names, then you need to go with the analytical expression count(*) over(...) :

select
  custName,
   itemName,
   yearsUsed,
   bidPrice
from (
  SELECT 
    c.custName,
    ac.itemName,
    ac.yearsUsed,
    ac.bidPrice,
    count(*) over (partition by 
                   ac.itemName, 
                   ac.yearsUsed, 
                   ac.bidPrice) cnt
  FROM 
   auction ac INNER JOIN
   customer c ON c.custId = ac.custId 
)
where
  cnt > 1

see also this SQL fiddle

Answer 2

Try like this

     SELECT 
ac.itemName,
ac.yearsUsed,
ac.bidPrice,
c.custName
 FROM auction ac 
LEFT JOIN customer c ON c.custId = ac.custId 
GROUP BY ac.itemName,ac.yearsUsed,ac.bidPrice 
HAVING COUNT(*) > 1;

Answer 3

cust_id is missing from the inner select . By why use an inner select ?

select ac.itemname
,      ac.yearsused
,      ac.bidprice
from   auction ac
inner
join   customer c
on     c.custid = ac.custid
group
by     ac.itemname
,      ac.yearsused
,      ac.bidprice
having count(*) > 1
;