SQL Query to find out the frequency of each element in a column

Suppose we have a table "Person" as:

Id	LastName	FirstName	Age	City
1	Smith	John	33	Newyork
2	Smith	Mike	34	Boston
3	Paul	Ryan	39	Chicago
4	William	Brian	45	Baltimore
5	Rao	Sunita	41	Dayton
6	Zing	Sue	33	Owings Mills
7	Smith	Robert	45	Newyork
8	Paul	Zean	33	Chicago
9	Srivastava	Hemant	33	Baltimore
10	Rao	Venkat	45	Dayton

and we need to find out the frequency of the each age.

   SELECT Age, COUNT(Age)AS Frequency    

   FROM Persons   

   GROUP BY Age   

   ORDER BY    

   COUNT(Age) DESC

We get following result:

Age	Frequency
33	4
45	3
34	1
39	1

Now suppose we want to get the ‘Age’ which occurs more than equal to 2. For this query, we need to add HAVING clause after GROUP BY clause.

SELECT Age, COUNT(Age)AS Frequency

FROM Persons

GROUP BY Age 

HAVING  COUNT(Age) >= 2

That gives result as:

Age	Frequency
33	4
45	3