I also consider that these two SQL scripts are completely different and thus shouldnt be considered alternatives for each other
SELECT PostCode, COUNT(Postcode)
FROM
(
SELECT DISTINCT Address1, Address2, City, Postcode
FROM AddressTable
) AS Sub
GROUP BY Postcode
HAVING COUNT(Postcode) > 1
and
SELECT Address1,Address2,City,PostCode,Count(PostCode)
FROM AddressTable
GROUP BY Address1,Address2,City,PostCode
HAVING Count(PostCode) > 1
This. Can it be corrected in the original article?