RDBMS Concepts

Amisha Purswani
Last Updated: May 13, 2022

Introduction

RDBMS stands for Relational Database Management System. RDBMS is a database management system based on the relational model introduced by E.F Codd in the 1970s. The major DBMS like SQL, My-SQL, ORACLE are all based on the principles of relational DBMS. 

Commonly used terms in Relational Models

Widely used terms in Relational Model are - 

Table or Relation:  The table is also known as relation. The table consists of one or more columns and each column has a unique name. Each table contains a record of a particular type and each record type defines a fixed number of fields or attributes.

For Example:

Roll No

Name

Marks

Phone

001

AAAA

88

1111111111

002

BBBB

83

222222222

003

CCCC

98

333333333

004

DDDD

67

444444444

Tuple or record or row: Rows are called tuples in a relational database. These are also called records. In a relation there should not be two same tuples. One of the tuples can be represented by

001

AAAA

88

1111111111

Attributes: Attributes are nothing but columns in a relational database. They are also called Fields. For example, the above table consists of four attributes: RollNo, Name, Marks, and phone.

Relation Instance: It refers to a relational database that has some integrity constraints. For example- the following is a relation instance - which contains the records with age above 18.

Roll No

Name

Age

Adhar Card

1

Amisha

19

1111111111

2

Bhavisha

20

222222222

3

Charmi

19

333333333

Domain: For each attribute of the relational table, there is a set of valid values called domain. For example - in the above table, the domain of the Name attribute is all possible names of students. But the Domain of Age attributes is (19,20)

Atomic: The domain is atomic if elements of the domain are considered to be indivisible units. For example, in the above table, the attribute Adhar Card is non-atomic.

NULL attribute: A null is a special symbol, independent of data type, which means either unknown or inapplicable. It does not mean zero or blank. For example  - Consider a salary table that contains NULL.

EMP

Job Name

Salary 

Commission

E10

Sales

12500

32090

E11

Null

25000

8000

E12

Sales

44000

0

E13

Sales

44000

Null

Degree: It is nothing but the total number of columns present in the relational database. In a given Student table - Degree is 4

Roll No

Name

Marks

Phone

001

AAAA

88

1111111111

002

BBBB

83

222222222

003

CCCC

98

333333333

Cardinality: Cardinality is the number of tuples/rows present in the relational database. In the above-given table, the cardinality is 3.

Integrity Constraints

Constraints mean some rules or restrictions that are set on the database. Integrity constraints are rules that are to be applied to the database columns to ensure the validity of data.

There are four types of integrity constraints that are followed for RDBMS:

  1. Entity integrity Constraints:  It specifies that there should be no duplicate rows in a table.
  2. Domain Integrity Constraints: It tells the column’s/attribute’s valid values.
  3. Referential Integrity Constraints: It corresponds to the foreign key concept and hence provides several constraints for inserting, deleting, and modifying content in the referenced relation or referencing relation.
  4. User-Defined Integrity: It enforces some specific business rules that are defined by users. These rules are different from the entity, domain, or referential integrity.

Advantages of RDBMS:

  1. Structural Independence: Structural independence is an ability that allows us to make changes in one database without affecting another. The relational model has structural independence. Hence making required changes in the database is convenient in the relational database model.
  2. Data Security: Data Security is critical when data sharing is private. RDBMS provides Data Security.
  3. Query capability: Using simple query language (such as SQL) users can get desired information from the database.
  4. Easy to maintain and use: RDBMS is flexible with multiple data. Hence easy to maintain and use.

Disadvantages of RDBMS:

  1. The relational model requires powerful hardware and large data storage devices.
  2. May lead to a slower processing time.
  3. Poorly designed systems lead to poor implementations of database systems. 

FAQs

  1. What is RDBMS?
    RDBMS is a database management system that stores data in form of tables having unique names and each table contains rows/tuples and columns/attributes. Tables in RDBMS have a primary key identifier, and data values are kept in the form of tables.
     
  2. What are some examples of RDBMS?
    The major DBMS like SQL, My-SQL, ORACLE are all based on the principles of relational DBMS. 
     
  3. What is the difference between RDBMS and DBMS?
    DBMS stores data as files while RDBMS stores data in a tabular manner.
     
  4. Why is RDBMS used?
    For the purposes of ACID, the integrity constraint is defined by the RDBMS. To retrieve the stored information, the RDBMS system supports a tabular structure of the data and a relationship between them. An RDBMS is built to handle massive amounts of data. It can be used by numerous people.

Key Takeaways

In this blog, we have learned that RDBMS stands for Relational Database Management System. RDBMS is a database management system based on the relational model introduced by E.F Codd in the 1970s. The major DBMS like SQL, My-SQL, ORACLE are all based on principles of relational DBMS. Then we learned about various terms used in RDBMS like Table, Tuple, Attributes, Relation, Atomic, Degree, Cardinality, etc. Integrity constraints are rules that are to be applied to the database columns to ensure the validity of data. There are four types of integrity constraints that are followed for RDBMS: entity, domain, user-defined and referential.

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