How can I write a SQL query that finds all entries in the database where a particular column occurs twice or more?

Question

I have a table called Laptop that has a column named "HD". How can I write a query that will find all "HD" entries that occur twice or more?

[HD]
10
20
20
40
50
10

So, out of those entries in HD, the query will return 10, and 20 because they both occur twice or more.

Answer 1

This is surely a duplicate, but couldn't find it. Anyhow, you do it with the HAVING clause after an aggregate.

SELECT HD,COUNT(HD) FROM Laptop GROUP BY HD HAVING COUNT(HD) > 1

Answer 2

select HD from LapTop group by HD having count(*)>1

Answer 3

SELECT HD, count(HD) FROM LAPTOP GROUP BY HD HAVING COUNT(HD) > 1