Normally we want to fetch this information that which row have duplicate value.So here i am sharing very easy solution for this.by using this query you can get which row have multiple entries.
SELECT surname, COUNT(surname) AS numOftimes FROM employee GROUP BY surname HAVING ( COUNT(surname) > 1 )
You could also use this technique to find rows that occur exactly once or n time:
SELECT surname FROM employee GROUP BY surname HAVING ( COUNT(surname) = 1 )
or for 'n' timesSELECT surname FROM employee GROUP BY surname HAVING ( COUNT(surname) = n )