You can use a WHERE clause in a statement with GROUP BY. The WHERE clause is evaluated before the GROUP BY clause. Rows that do not satisfy the conditions in the WHERE clause are eliminated before any grouping is done. Here is an example:

SELECT  Name, AVG( UnitPrice )
   FROM Products
   WHERE ID > 400
   GROUP BY Name;

Only the rows with ID values of more than 400 are included in the groups that are used to produce the query results.

 Example

SELECT Name, SUM( Quantity )
   FROM Products
   WHERE Name LIKE '%shirt%'
   GROUP BY Name
   HAVING SUM( Quantity ) > 100;