Remove Duplicate Rows HAVING ( COUNT(*) > 1 )

Finding duplicates in a table.  Find all email addresses that exist more than one time:

SELECT customer,

 COUNT(customer) AS NumOccurrences

FROM SalesTable

GROUP BY customer

HAVING ( COUNT(customer) > 1 )

Find rows that occur exactly once:

SELECT customer

FROM SalesTable

GROUP BY customer

HAVING ( COUNT(customer) = 1 )