SQL - select rows that have the same value in two columns

Question

The solution to the topic is evading me.

I have a table looking like (beyond other fields that have nothing to do with my question):

NAME,CARDNUMBER,MEMBERTY

Answer 1

Since you mentioned names can be duplicated, and that a duplicate name still means is a different person and should show up in the result set, we need to use a GROUP BY HAVING COUNT(*) > 1 in order to truly detect dupes. Then join this back to the main table to get your full result list.

Also since from your comments, it sounds like you are wrapping this into a view, you'll need to separate out the subquery.

CREATE VIEW DUP_CARDS
AS
SELECT CARDNUMBER, MEMBERTYPE
FROM mytable t2
GROUP BY CARDNUMBER, MEMBERTYPE
HAVING COUNT(*) > 1

CREATE VIEW DUP_ROWS
AS
SELECT t1.*
FROM mytable AS t1
INNER JOIN DUP_CARDS AS DUP
ON (T1.CARDNUMBER = DUP.CARDNUMBER AND T1.MEMBERTYPE = DUP.MEMBERTYPE )

SQL Fiddle Example