Sometimes displaying data directly from the database is not enough. You need to transform the raw data into useful information that end-users can understand. An example is calculating the time to fulfill an order.
To add a new attribute with a calculated value to an aggregate:
Set the name of the new attribute;
While the column is still selected, click 'Add formula' in it, or double-click on the 'Value' property;
Write an expression that calculates the result.
To fetch information about the new orders, and for how many days they are waiting to be shipped:
Aggregate a Column into a Single Value | Segment Identical Data into Groups