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    Codd’s Rules of DBMS

    Dr E.F. Codd, the father of relational database framework, defines a set of rules that were intended to describe the essential characteristics and capabilities of any relational system. Codd proposed 13 rules famous called a Codd’s 13 (0-12) rules to check the DBMS concept toward his relational model. Codd’s rule describes what exceptional a DBMS requires to emerge a Relational Database Management System (RDBMS).

    The Codd’s 13 rules (0 to 12) for the relational databases are as follows:

    DBMS Codd’s Rules

    Rule 0: Foundation Rule

    A relational database management system must handle the database entirely through its relational capabilities.

    Rule 1: Information Rule

    All data in a relational database, including table names, column names are defined logically through values in tables. Customer productivity is progressed since knowledge of only one language is necessary to access all information such as the description of the table and attribute meaning, integrity constraints. Action can be appropriated when the limitations are disrupted.

    Rule 2: Guaranteed Access Rule

    Each and every value in the relational database is assured to be feasible via utilizing a consolidation of the table name, primary key value, and column name.

    Rule 3: Systematic Treatment of NULL Values

    The DBMS provides systematic support for handling null values, distinct from default values, and independent of any domain. A null value means that data is not there, is not known or is irrelevant. The null values represent empty database fields.

    Rule 4: Active Online Catalog

    The database description is described at the logical level in a similar technique or ordinary information so that the authorized client can apply the similar relational language to its interrogation as they apply to the regular information. In a relational database, the same query language is utilized on the data dictionary as is used on the function database. This means users and programmers need only known one data language (such as SQL) to operate on the entire database.

    Rule 5: Comprehensive Data sub-language Rule

    The relational database management system may provide several languages. But at least one of them should permit the user to do all the following: define tables and views, query and update data, set integrity constraints, set authorizations and define transactions. Customer productivity is upgraded because there is just one approach that can be used for all database operations.

    There are often many different ways for interacting with the database, for example, QBE or SQL. Regardless of what user interaction is used, any relational DBMS should have one well-defined language. This data language should be capable of doing all the activities in the rule. SQL is such a language. It does a reasonable job of supporting these activities.

    Rule 6: View Updating Rule

    The framework also updates all views that are theoretically updated. A view is a virtual table in the database. A view does not occur in its own right but develops to the user as if it does. With a relational DBMS, any change that a user makes to view should ideally also be made in the base table from which the view is derived.

    Rule 7: High-level Insertion, Updation and Deletion

    The potential of management with a base relation or a derivative relation as an original operand spread not only to the recovery of record but further the inserting, updating, and deleting of information. This phase that one command in a relational database should be adequate to carry out an operation on one or more rows in either a base relation or a view.

    Rule 8: Physical Data Independence

    Application software and terminal action continue logically unimpaired at whatever time any transforms are built in one or other storage description or access technique. This rule states that physical changes, such as the following, should not affect existing applications:

    1. Moving tables to different disk drives
    2. Changing the order of rows in table
    3. Reorganizing the database files

    In a relational environment, the DBMS must decide how to access a piece of data. If the user or programmer wishes to access a particular part of data, they must specify the following information:

    1. The Table Name
    2. The Column Name
    3. The Primary Key

    Rule 9: Logical Data Independence

    Application software and terminal action continue logically unimpaired though data-secure transform of any generous that theoretically authorize unimpaired are made to the base tables. A relational table may have to be expanded or restricted. New tables may also be added to the database. Expansion of the table may involve adding columns to existing tables. According to Rule9, the addition of a new column to the table in a relational database should not affect the program that uses the table. The other type of changes covered here is the restructuring of tables.

    Rule 10: Integrity Independence

    The database language must be capable of describing integrity rules. They must be stored in the outline catalogue, and they cannot be avoided. Integrity control must exist to protect the consistency of the database from unauthorized users. Two integrity constraints exist.

    1. Entity Integrity
    2. Referential Integrity

    Rule 11: Distributed Independence

    Application software and Adhoc requests are not affected by modifying the distribution of physical information. This enhances systems reliability since application software will work even if the software and data are moved to different sites.

    Rule 12: Non-Subversion Rule

    If a low-level procedural language is supported, it must not be able to ignore integrity or security constraints expressed in the high-level relational language.


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