Codd's rules | Article about Codd's rules by The Free Dictionary
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Codd's rulesThirteen rules numbered 0 through 12 that verify whether a relational database management system (RDBMS) is truly relational. The rules deal with how data are organized, modified and accessed. For example, Rule 2 requires every value to be accessible by table name, primary key value and column name. Rule 11 requires that users see the database as singular even if it is distributed across multiple sites. See laws.