Topic: How correctly to work with calculated fields?
Normal situation: in the table there are fields for overall dimensions of some goods (length, width and height), but it is required as well volume.
Entering into the table a special field volume, we, as a matter of fact, create surplus information and we risk that the data in the table can and be mismatched. On the other hand, now it is necessary to create a special field and in a special way it to process.
The method which to me is known, it to add a superfluous field in request approximately so:
SELECT length, width, height, (length * width * height) as volume FROM table
Whether however the calculated field will operatively change at change of fields of the linear sizes and whether there will be complexities with saving of results?
Besides, in Lazarus there was a special type of fields, and named: the calculated. They were not mentioned even in the text of requests (i.e. the request would be such: SELECT length, width, height FROM table) also were present only at lists of fields inspectors of request. But every time when in the program there would be a change of normal fields of request, special event in which it was possible to register calculation and assignment for a field volume was initiated. It, including, allowed to do without the description superfluous retrieval arguments request (if they were required for field calculations). Whether there is an analog in PowerBuilder?
And the general question such: as though you implemented such task?