How to Find Rows which are Duplicates by a Key but Not Duplicates in All Columns?

Question

I am working with a table which is an extract of a set of other tables. All of the rows of the extract table should be unique according to keys D1, D2 and D3. They are not.

Answer 1

This would have performance limitations, but is much easier to understand:

SELECT D1, D2, D3
FROM TEST_KEY TK
WHERE (D1, D2, D3) IN
        (SELECT D1, D2, D3 FROM TEST_KEY TK2
         GROUP BY D1, D2, D3
         HAVING COUNT(*) > 1)
  AND (D1, D2, D3) IN
        (SELECT D1, D2, D3 FROM TEST_KEY TK2
         GROUP BY D1, D2, D3, C4, C5, C6
         HAVING COUNT(*) < 2)

Unable to test on SQL-Server, hope the syntax is good.

Again, not sure if you have analytic functions in SQL-Server, but this one works in Oracle and might be faster:

WITH BAD_DUP AS (
SELECT TK.*,
       COUNT(1) OVER (PARTITION BY D1, D2, D3, C4, C5, C6 ORDER BY D1) FULL_DUP,
       COUNT(1) OVER (PARTITION BY D1, D2, D3 ORDER BY D1) KEY_DUP
FROM TEST_KEY TK)
SELECT * FROM BAD_DUP
WHERE FULL_DUP < KEY_DUP

Would like to get it down to a single query....