Sep 29

Rules for a Relational Database

The Most popular database module is a relational database module which is develop by Dr. E. F. Codd in 1970.  This rules proved that database relational or not. Dr. Codd develop 13 rules for relational database module but 12 rules are enough to prove the relational database module.

Followings are Rules for relational database module.

Rule Zero
The Foundation rule: A relational DBMS must be able to manage databases entirely through its relational capabilities.

Rule 1
Information rule:- All information in a relational database (including table and column names) is represented explicitly as values in tables.

Rule 2
Guaranteed access:-Every value in a relational database is guaranteed to be accessible by using a combination of the table name, primary key value, and column name.

Rule 3
Systematic null value support:-The DBMS provides systematic support for the treatment of null values (unknown or inapplicable data), distinct from default values, and independent of any domain.

Rule 4
Active, online relational catalog:-The description of the database and its contents is represented at the logical level as tables and can therefore be queried using the database language.

Rule 5
Comprehensive data sub language:-At least one supported language must have a well-defined syntax and be comprehensive. It must support data definition, manipulation, integrity rules, authorization, and transactions.

Rule 6
View updating rule:-All views that are theoretically updatable can be updated through the system.

Rule 7
Set-level insertion, update, and deletion:-The DBMS supports not only set-level retrievals but also set-level inserts, updates, and deletes.

Rule 8
Physical data independence:-Application programs and ad hoc programs are logically unaffected when physical access methods or storage structures are altered.

Rule 9
Logical data independence:-Application programs and ad hoc programs are logically unaffected, to the extent possible, when changes are made to the table structures.

Rule 10
Integrity independence:-The database language must be capable of defining integrity rules. They must be stored in the online catalog, and they cannot be bypassed.

Rule 11
Distribution independence:-Application programs and ad hoc requests are logically unaffected when data is first distributed or when it is redistributed.

Rule 12
Non subversion:-It must not be possible to bypass the integrity rules defined through the database language by using lower-level languages.

Codd’s idea for an RDBMS uses the mathematical concepts of relational algebra to break down data into sets and related common subsets.



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