What is Filter groups with HAVING

When you have created groups with a GROUP BY clause, you can further filter the results. The HAVING clause acts as a filter on groups. This is similar to the way that the WHERE clause acts as a filter on rows returned by the FROM clause.

A HAVING clause enables you to create a search condition, conceptually similar to the predicate of a WHERE clause, which then tests each group returned by the GROUP BY clause.

The following example counts the orders for each customer, and filters the results to include only customers that have placed more than 10 orders:

SQLCopy

SELECT CustomerID,
      COUNT(*) AS OrderCount
FROM Sales.SalesOrderHeader
GROUP BY CustomerID
HAVING COUNT(*) > 10;