Use HAVING with Aggregate Functions

Unlike the WHERE clause, HAVING can be used with aggregate functions.

An aggregate function is a function where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning or measurement (Wikipedia).

Common aggregate functions include COUNT(), SUM(), MIN(), and MAX().

This example uses the Car Table from the Example Databases.

SELECT CustomerId, COUNT(Id) AS [Number of Cars]
FROM Cars
GROUP BY CustomerId
HAVING COUNT(Id) > 1

This query will return the CustomerId and Number of Cars count of any customer who has more than one car. In this case, the only customer who has more than one car is Customer #1.

The results will look like:

CustomerId | Number of Cars | ––––– | ––––––– | 1 | 2 |