Creating a computation

Start by creating a normal text item on the form that was created in the second recipe of the first chapter. This is a normal form based on the EMP table. Normally, a user would have to manually enter the commission. What we are going to do is to create a computation that will automatically enter an amount into this field, based on a percentage of the salary and a bonus for people that work in the Sales department.

First, identify the item that holds the commission column.

The next step is to find the moment when we want to execute the computation. In this case, before the page is submitted but after the Save button is pressed. So in this case we will create the computation After Submit.

The computation is now done. It can be tested by selecting an existing record from the list of employees and altering its salary and then saving the data. Another option is to create a completely new employee. You will see that an employee under the Sales department with dept no. 30 will receive a 10 percent commission whilst employees from all other departments will receive 5 percent.

Computations can be used for far more situations than preparing an item before saving it to the database.

An example of another implementation can be an item that will show the current date when the page loads, or an item that will show a total amount when certain other amount items are entered. Used with dynamic actions, computations can be very powerful.