How to filter inconsistent records in sqlite

Say I have SQLite table with the following records:

recID	productID	productName
1	1	Product A
2	2	Product B
3	2	Product C
4	3	Product D
5	3	Product D

recID = primary key, auto increment.

If I run:

SELECT productID, productName 
FROM table 
GROUP BY productID, productName

Result is:

productID	productName
1	Product A
2	Product B
2	Product C
3	Product D

As you can see, productID 2 has inconsistent productName: Product B and Product C. How do I run query just to detect the inconsistent ones? Eg I want the result to be:

productID	productName
2	Product B
2	Product C

Answer

Use EXISTS to get a productID with more than 1 productNames:

SELECT t1.productID, t1.productName 
FROM tablename t1
WHERE EXISTS (
  SELECT *
  FROM tablename t2
  WHERE t2.productID = t1.productID AND t2.productName <> t1.productName 
);

Or, for a small dataset use aggregation in a subquery which counts the distinct number of productNames of each productID, with the operator IN:

SELECT productID, productName 
FROM tablename
WHERE productID IN (
  SELECT productID
  FROM tablename
  GROUP BY productID
  HAVING COUNT(DISTINCT productName) > 1
);