Bad Design—What Not to Do - Database Design for Mere Mortals - page 408

Figure 14.1. An example of a flat-file structure
This diagram represents the structure of a single table. (Imagine how other tables within
the database are structured!) You can readily see that this structure will inevitably cause
problems with redundant data and inconsistent data and that it suffers from a lack of data
integrity. As you've probably already noted, there are a few other problems with this struc-
ture.
• Multipart fields : S ALES R EP N AME includes the sales rep's first and last names,
C USTOMER N AME includes the customer's first and last names, and C USTOMER
A DDRESS includes the customer's street address, city, state, and zip code.
• Calculated fields: The O RDER A MOUNT field contains a value that is most likely
manually calculated, especially if the customer is ordering more than three items.
The I TEM # E XTENSION fields are also all likely to be manually calculated. The
value for a given I TEM # E XTENSION field is the result of multiplying the value of a
related Q UANTITY # field by the value of a related P RICE # field. (For example:
I TEM 3 E XTENSION = Q UANTITY 3 ∴ P RICE 3)