Group By and Having Clause

GROUP BY is used in conjunction with aggregate functions such as SUM() or MIN().  For example, let's say you have a table that has data on student name and test score.  To find out the total score for each student, you'll use the SUM() function together with the GROUP BY function as follows:

SELECT student_name, SUM(score)
FROM test_scores
GROUP BY student_name;

HAVING is a condition that can be placed on top of an aggregate function.  In the above example, you can add "HAVING SUM(score) > 300" at the end of the query so the query only returns students whose total score is higher than 300.

Hi Anilkumar

please refer:

http://www.sql-tutorial.net/SQL-HAVING.asp

http://www.sql-tutorial.net/SQL-GROUP-BY.asp

In simple

GROUP BY  combines those rows into groups
HAVING  filters groups

check the following for reference and example

http://www.w3schools.com/sql/sql_groupby.asp

http://www.w3schools.com/sql/sql_having.asp