Codds twelve rules are a set of thirteen rules numbered zero to twelve proposed by edgar f. Codd wrote 12 rules for defining relational database management systems rdbms, which revolutionized the it industry allowing data management. Home page title page jj ii j i page 2 of 15 go back full screen close quit codd s rules 1985 proposed to test dbmss for con. This rule requires that a relational database be selfdescribing. The database description is represented at the logical level in the same way as ordinary data, so authorized users can apply the same relational language to its interrogation as they apply to regular data.
Codd, after his extensive research on the relational model of database systems, came up with twelve rules of his own, which according to him, a database must obey in order to be regarded as a true relational database. In 1985, dr edgar frank ted codd a computer scientist working for ibm proposed the relational model for database management which forms the theoretical basis for relational databases. This rule is essentially a restatement of the fundamental requirement for primary keys. Codd, the founder of the relational database systems, framed twelve rules to assist a database product to qualify as relational. These rules are developed by dr edgar f codd ef codd in 1985 to define a perfect rdbms. Codds 12 rules is a set of rules that a database management system dbms must satisfy if its to be considered relational i. All information in the database is to be represented in one and only one way, namely by values in column positions within rows of tables. For a system to qualify as an rdbms it must be able to manage its databases entirely through its relational capabilities. Codd s 12 rules is actually a set of thirteen rules, numbered from zero to twelve. Codd, who is considered a pioneer of the relational database model. An rdbms product has to satisfy at least six of the 12 rules of codd to be accepted as a fullfledged rdbms. Codd, proposed thirteen rules and said that if a database management system meets these rules, it can be called as a relational. Codd proposed rules for relational database model popularly known as codds 12 rules to test dbmss concept against his relational model. It is therefore a basic rule in relational databases that there should be no pointers at all in the.
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