The Definitive Guide to SQLite

APPENDIX CCodd's 12 Rules

The following rules are taken directly from Codd's 1985 article, "Is your DBMS really relational?" in Computerworld magazine. They describe the essential characteristics of the relational model. All of these rules are covered in detail in Chapter 3.

1. Rule Zero:

   For any system that is advertised as, or claimed to be, a relational data base management system, that system must be able to manage data bases entirely through its relational capabilities.

2. The information rule:

   All information in a relational data base is represented explicitly at the logical level and in exactly one way—by values in tables.

3. The guaranteed access rule:

   Each and every datum (atomic value) in a relational data base is guaranteed to be logically ...