RDBMS stands for Relational Database Management Systems.
A Relational Database Management System (RDBMS) is a database management system (DBMS) based on the relational model introduced by Dr. Edgar F. Codd.
Dr. E. F. Codd written 12 RDBMS rules and strictly speaking all RDBMS should satisfy codd’s 12 rules, but in practice there is no DBMS that satisfy all these rules.
Relational Database Management System (RDBMS) stored data in form of related tables. RDBMS are powerful because they require few assumptions about how data is related or how it will be extracted from the database.
First RDBMS implementation of relational model was Multics Relational Data Store, 1st sold in 1978.
Today, most popular commercial RDBMS are Oracle, Sybase SQL Server, IBM’s DB2, Microsoft SQL Server.
There are some powerful free or open source RDBMS, commonly used MySQL and PostgreSQL.
RDBMS Rules by Dr. E. F. Codd
Rule 1: The Information Rule
All data should be presented in table form.
Rule 2: Guaranteed Access Rule
All data should be accessible without ambiguity. This can be accomplished through a combination of the table name, primary key, and column name.
Rule 3: Systematic Treatment of Null Values
A field should be allowed to remain empty. This involves the support of a null value, which is distinct from an empty string or a number with a value of zero.
Rule 4: Dynamic On-Line CatLog based on the Relational Model
A relational database must provide access to its structure through the same tools that are used to access the data.
Rule 5:Comprehensive Data Sub language Rule
The database must support at least one clearly defined language that include functionality for data definition, data manipulation, data integrity, and database transaction control.
Rule 6: View Updating Rule
Data can be presented in different logical combinations called views. Each view should support the same full range of data manipulation that has direct access to a table available.
Rule 7: High-level Insert, Update, and Delete
Data can be retrieved from a relational database in sets constructed of data from multiple rows and /or multiple tables.
Rule 8: Physical Data Independence
The user is isolated from the physical method of storing and retrieving information from the database.
Rule 9: Logical Data Independence
How data is viewed should not be changed when the logical structure (table’s structure) of the database integrity.
Rule 10: Integrity Independence
The database language should support constraints on user input that maintain database integrity.
Rule 11: Distribution Independence
A user should be totally unaware of whether or not the database is distributed (whether parts of the database exist in multiple locations).
Rule 12: Non subversion Rule
There should be no way to modify the database structure other than through the multiple row database language (like SQL).
DBMS Vs RDBMS
|In DBMS relationship between two tables or files are maintained programmatically||In RDBMS relationship between two tables or files can be specified at the time of table creation|
|DBMS does not support Client/Server Architecture||Most of the RDBMS support Client/Server Architecture|
|DBMS does not support Distributed databases||Most of the RDBMS supports Distributed database|
|In DBMS there is no security of data||In RDBMS there are multiple level of security
1. Logging in at OS level
2. Command level
3. Object level
|Each table is given an extension in DBMS||Many tables are grouped in one database in RDBMS|
|DBMS may satisfy less than 7 to 8 rules of Dr. E F Codd||RDBMS usually satisfy more than 7 to 8 rules of Dr. E F Codd|
|Record||Row, Tuple, Entity|
|File||Table, Relation, Entity Class|