August 2009
Intermediate to advanced
893 pages
26h 48m
English
Content preview from Database Systems: Concepts, Design and Applications
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5.2. Codd’s Rules
Dr. Edgar F. Codd proposed a set of rules that were intended to define the important characteristics and capabilities of any relational system [Codd 1986]. Today, Codd’s rules are used as a yardstick for what can be expected from a conventional relational DBMS. Though, it is referred to as “Codd’s twelve rules”, in reality there are thirteen rules. The Codd’s rules are summarised in Table 5.1.
| Rule | Rule Name | Description |
|---|---|---|
| Rule 0 | Foundation Rule | A relational database management system must manage the database entirely through its relational capabilities. |
| Rule 1 | Information Rule | All information is represented logically by values in tables. |
| Rule 2 | Guaranteed Access Rule | Every data value is logically accessible by a combination ... |