Question

I’m trying to check whether certain features in Product A are all also featured in Product B. We count the amount of how many such Product B’s there are that fully fulfill all of the features of Product A.

My query returns the correct value for the Count, however, I want it to display 0 where there are no such Product B’s that have the features of Product A. At the moment, it is only returning the values where the count is greater than 1.

For a further explanation please refer to the following code:

SELECT P1.Product_ID, COUNT(P2.Product_ID) AS NUMBER
FROM Products P1, PRODUCTS P2
WHERE P1.Product_ID != P2.Product_ID 
      AND
NOT EXISTS (
            ( SELECT FEATURELIST.feature_id
              FROM FEATURELIST
              WHERE FEATURELIST.Product_ID = P1.Product_ID)
              MINUS
            ( SELECT FEATURELIST.feature_id
              FROM FEATURELIST
              WHERE FEATURELIST.Product_ID = P2.Product_ID )
            )
GROUP BY P1.PNO;

This returns something that looks like:

Product_ID    |    NUMBER
1                    2
5                    7
13                   2
17                   4

I want it to return the full Product_ID list.. so something like this:

    Product_ID    |    NUMBER
     1                    2
     2                    0
     3                    0
     4                    0
     5                    7
     6                    0
     7                    0
     ..                   ..
     17                   4

Using oracle sql.

Answer 1

A simple solution might be to UNION all products with a default COUNT of 0 and perform an additional GROUP BY on the results.

SELECT  P1.Product_ID, SUM(NUMBER) AS NUMBER
FROM    (
          SELECT  P1.Product_ID, 0 AS NUMBER
          FROM    Products P1
          UNION ALL
          SELECT  P1.Product_ID, COUNT(P2.Product_ID) AS NUMBER
          FROM    Products P1, PRODUCTS P2
          WHERE   P1.Product_ID != P2.Product_ID 
                  AND NOT EXISTS (
                      ( SELECT FEATURELIST.feature_id
                        FROM FEATURELIST
                        WHERE FEATURELIST.Product_ID = P1.Product_ID)
                        MINUS
                      ( SELECT FEATURELIST.feature_id
                        FROM FEATURELIST
                        WHERE FEATURELIST.Product_ID = P2.Product_ID )
                      )
          GROUP BY P1.PNO
        ) P1
GROUP BY
        P1.Product_ID