Finding duplicate values in a SQL table

Question

It\'s easy to find duplicates with one field:

SELECT name, COUNT(email) 
FROM users
GROUP BY email
HAVING COUNT(email) > 1

So if we have

Answer 1

A little late to the party but I found a really cool workaround to finding all duplicate IDs:

SELECT GROUP_CONCAT( id )
FROM users
GROUP BY email
HAVING ( COUNT(email) > 1 )