Performing aggregate operations

Next to the common SQL databases, hibernate allows us to perform an aggregate operation using a hibernate API. We can perform an aggregation operation such as sum, avg, min, max, count, and so on.

We will discuss the use of some aggregate functions by example.

Getting ready

To perform an aggregation operation, we will consider a predefined table structure with the data so that it's easy to understand how the aggregate functions work.

The predefined table and class structure we mentioned earlier can be found in two different classes, product and category, with their relationship. The following code and script can be used to create a Java class and a database table.

Creating the tables

Use the following script to create the tables if you are not using hbm2dll=create|update:

Use the following code to create the category table:

CREATE TABLE `category` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `created_on` datetime DEFAULT NULL,
  `name` varchar(255) DEFAULT NULL...