Aggregate Functions Part 1

Query.apex now supports the powerful aggregate functions. Features include 'count', 'countDistinct', 'max', 'min', 'avg', 'sum', 'group by' clauses, and even 'having' clauses.

A simple aggregate function can be:

List result =
    new Query('Account').
    max('NumberOfEmployees', 'maxEmployees').
    aggregate();

Its equivalent a static SOQL looks like this:

List result =
    [ SELECT Max(NumberOfEmployees) maxEmployees FROM Account ];

In this example, the query finds the maximum number in the NumberOfEmployees field of all available Accounts, and use 'maxEmployees' as an alias of the aggregate function.

As you can see, the return type is a list of AggregateResult, which is a standard Salesforce class. Since we are not using any 'group by' clauses, we can safely assume there is one and only one element in this list. To get the result of the aggregate function we can use the alias we just set.

List result =
    new Query('Account').
    max('NumberOfEmployees', 'maxEmployee').
    aggregate();

Integer maxEmployee = (Integer)result[0].get('maxEmployee');