When creating a report, you can define computed columns and computed fields as follows:
In the SQL Select painter, you can define computed columns when you are defining the SELECT statement that will be used to retrieve data into the report.
In the Report painter, you can define computed fields after you have defined the SELECT statement (or other data source).
When you define the computed column in the SQL Select painter, the value is calculated by the DBMS when the data is retrieved. The computed column’s value does not change until data has been updated and retrieved again.
When you define the computed field in the Report painter, the value of the column is calculated in the report after the data has been retrieved.