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Database Systems: Concepts, Design and Applications by S. K. Singh

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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.

Table 5.1. Codd’s rules
RuleRule NameDescription
Rule 0Foundation RuleA relational database management system must manage the database entirely through its relational capabilities.
Rule 1Information RuleAll information is represented logically by values in tables.
Rule 2Guaranteed Access RuleEvery data value is logically accessible by a combination ...

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