Determining characteristics of a database and its tables

For reasons of security, one simply must not rely on the user to know the database structure in order to make a query. Even if the user does, one should never write code that assumes this. You never know who the user is and what nefarious results will be sought by the user. Given that there are more people than you know who want to break your code and exploit your data, it is best practice to restrict the user's knowledge of the database and to verify the integrity of any data the end user inputs into the program.

Without doubt, the best way to restrict the user's knowledge of the database is to provide set options for the user in a way that the user cannot edit. In graphical user interfaces (GUIs), this is done most often by drop-down menus and radio buttons. In terminal-based programs, one lists the options. The former keeps the programmer in control of the environment and so funnels the user to the point of either choosing the set...