What is RDBMS? CODD'S Principles

In this post we are going to discuss about RDBMS and features of RDBMS and their CODD'S Rules.why we use RDBMS and importance of RDBMS.

Definition of RDBMS?

RDBMS is a Relational Data Base Management System or simply Relational DBMS. It was introduced by E.F.Codd which adds an additional condition that the system supports a tabular structure for the data with enforced relationships among the tables.

Features of RDBMS:

• The ability to create multiple tables and enter data into them.
• An interactive Query Language
• Retrieval of information stored in more than one table
• provides a catalog or Dictionary,which itself consists of tables

The table consists of rows and columns.

Operations:

SELECT: extracts specified rows from a table

PROJECT: extracts specified columns from a table

JOIN: joins together two tables on the basis of common values in a common column operations are all set-at-a-time and not row-at-a-time.

Catalog means consists of all the information of the various  schemas(external,conceptual,internal) and all of the corresponding mappings.

CODD'S Principles/Rules:

0. The Rule specifies the system must qualify as relational and use its relational  felicities to manage and access database.

1. All information in a relational database which includes table name,column names are represented by values in tables

2. Every quantify of data in a relational database can be accessed by using  combination of a table name, a primary key value which identifies the row and attribute name that is identified as a cell.

3. The RDBMS provides a mechanism which handles records that have unknown or inapplicable values in a pre-defined fashion

4. The information of a database and in its contents are database objects(tables)and therefore can be queried via the data manipulation language(DML)

5. A RDBMS system should allow user to do all of the following  Define tables and views,query and update the data,set integrity constraints,set authorizations and define transactions.

6. RDBMS provides a mechanism to update any view which is theoretically update-able  Data consistency is ensured, since the changes made in the views are transmitted to the original table and vice-versa.

7. The RDBMS provides mechanism for insertions,updation and deletion at a table level. The performance is improved since the commands act on a set of records rather than one record at a time.

Read also: Normalization in Database