Data that are Results
Even though it might seem natural to have a distinct element for the total_price of the car, in practice this is not justified. The reason is that the total price is a computed result. Having the total price printed on a sales contract constitutes an output. Thus, we eliminate this information in the list of column names. For the same reason, we could omit the tax column because it can be computed.
By removing the total price column, we could encounter a pitfall. We have to be sure that we can reconstruct this total price from other sub-total elements, now and in the future. This might not be possible for a number of reasons:
- The total price includes an amount located in another table, and this table will change over time (for ...
Get Creating your MySQL Database: Practical Design Tips and Techniques now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
