Codd’s Rules


Codd’s rules are a set of thirteen rules, proposed by Edgar F. Codd, which have to be satisfied by an operation or system to qualify as a relational database management system (RDBMS). These rules are essentially guidelines that outline how a truly relational database should behave for creating, processing and retrieving data. The rules cover aspects like data representation, data manipulation, comprehensive data sublanguage, and integrity independence among others.


The phonetics of the keyword “Codd’s Rules” is: /kɒdz ruːlz/

Key Takeaways

<ol> <li>Codd’s Rules are a set of thirteen rules that define what makes a DBMS relational. These rules were proposed by E.F. Codd, who is considered the pioneer of the relational model for databases.</li> <li>Each rule is designed in such a way that it represents the definition of the relational database system. So, a system that is fully relational should be able to manage databases entirely through its relational capabilities.</li> <li>The rules cover aspects like information presentation, data accessibility, data schema, null values, data language, and more. They set the foundation for creating an effective and efficient relational database management system.</li></ol>


Codd’s Rules, formulated by the English computer scientist Dr. Edgar F. Codd, are crucial in the field of technology as they provide a comprehensive framework for defining and evaluating the functionality of a relational database management system (RDBMS). They are fundamental to ensuring that databases operate correctly, efficiently and effectively. These 13 rules form a critical checklist for evaluating the capabilities and compatibility of RDBMS, thereby determining whether it can manage data in a consistent and accurate manner. Furthermore, they significantly contribute towards maintaining data integrity, and achieving database normalization. Adherence to Codd’s rules ensures that databases are flexible, robust and capable of handling complex data operations with accuracy and rapidity.


Codd’s Rules are a set of guidelines proposed by Dr. Edgar F. Codd, a researcher at IBM, to define what qualifies as a relational database system. These rules essentially serve as a yardstick for the evaluation of database management systems and their functionalities. The purpose of these rules is to ensure the integrity, consistency, and accuracy of data in a relational database, as well as to guide the operations and transactions carried out in these databases.Codd’s Rules guide how properly structured data should be manipulated and accessed, and they establish requirements for comprehensive management and administration of databases, including data protection, access control, and system management. Furthermore, these rules guide the implementation of SQL and other structured query languages used for querying and manipulating data. Therefore, Codd’s Rules have a significant role in database design, implementation, management, and data manipulation.


Codd’s Rules pertain to relational database management systems (RDBMS). These rules were proposed by Edgar F. Codd, a British computer scientist, to define what qualifies as a RDBMS. Here are three real-world examples related to Codd’s Rules:1. Oracle Database: This system follows Codd’s rules and is therefore a relational database. It supports multiple data models, including network-based and hierarchical data models. Its framework is designed around the relational model, thus satisfying Codd’s rule that every stored item should be logically addressable.2. MySQL: Another real-world example of an application that uses Codd’s rules is MySQL, which is an open-source RDBMS. MySQL follows Codd’s rules like the comprehensive data sub-language rule, where the system must support at least one relational language that has a linear syntax, can be used both interactively and within application programs, and can support data definition operations, data manipulation operations, security and integrity constraints.3. Microsoft SQL Server: Microsoft SQL Server is a relational database management system developed by Microsoft. As a RDBMS, it provides support for an assortment of Codd’s rules such as the guarantee of data consistency, ensuring that a specific level of isolation exists among multiple users, implementing multiple views for different users, and allowing changes in data without affecting the schema.

Frequently Asked Questions(FAQ)

**Q: Who developed Codd’s Rules?**A: Codd’s Rules were developed by Dr. Edgar F. Codd, a British computer scientist, who formulated a series of rules that define what a Database Management System (DBMS) needs to qualify as a Relational Database Management System (RDBMS).**Q: What is the significance of Codd’s Rules in Database Management Systems?**A: Codd’s Rules are significant because they serve as a guiding framework for database vendors in order to qualify their solutions as truly relational Database Management Systems (RDBMS).**Q: How many rules does Codd’s Rules comprise of?**A: Codd’s Rules consists of 13 rules, each one identifying a certain feature that a DBMS must have in order to be defined as a fully relational system.**Q: What is rule zero in Codd’s Rules?**A: Rule Zero states that a database management system must manage its stored data using only its relational capabilities, regardless of its application. This implies that the system should be fully relational, thereby standing on its own without the assistance of any non-relational extensions.**Q: Can you give an example of another rule from Codd’s Rules?**A: Sure. Codd’s Rule 12, also known as the “non-subversion rule” states: If a system provides a low-level language, that language must not be used to subvert or bypass the integrity rules and constraints expressed in the higher-level relational language.**Q: Do all DBMS follow Codd’s Rules?”A: No, not all DBMS follow all of Codd’s rules. In fact, no existing DBMS follows all 13 rules. However, those DBMS that closely follow most of Codd’s Rules are considered to provide a higher level of data integrity and independence.**Q: How applicable are Codd’s Rules in today’s database system?**A: Despite some changes and adjustments over the years, many of Codd’s Rules still apply and are relevant to modern database technology. They continue to be used to guide the development of RDBMS and influence RDBMS solutions.

Related Finance Terms

  • Relational Database
  • Data Independence
  • Normalization
  • Comprehensive Data Sub-language
  • Physical Data Independence

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