SQL Query To Obtain Value that Occurs more than once

Question

I need to query my database to show the records inside my table where lastname occurs more than three times. Example: in my Students Table, there are 3 people with Lastname

Answer 1

For SQL Server 2005+

;WITH T AS
(
SELECT *, 
       COUNT(*) OVER (PARTITION BY Lastname) as Cnt
FROM Students
)
SELECT * /*TODO: Add column list. Don't use "*"                   */
FROM T
WHERE Cnt >= 3