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What is a relational database in DBMS?

What is a relational database in DBMS?

A relational database is a type of database that stores and organizes data in tables, where each table consists of rows and columns. A relational database is based on the relational model, which is a logical representation of how data is related to each other. A relational database management system (RDBMS) is a software program that allows users to create, manipulate, and query relational databases using a standard language called SQL (Structured Query Language).

Relational Model

The relational model was proposed by E.F. Codd in 1970 as a way to simplify the management of data in databases. The relational model has the following features:

  • Data is represented as a collection of relations, or tables, where each table has a name and a set of attributes, or columns.
  • Each row in a table is called a tuple, or a record, and represents an instance of the entity that the table describes. Each tuple has a value for each attribute of the table.
  • Each attribute has a domain, or a set of possible values, and a data type, such as integer, string, date, etc.
  • Each table has a primary key, which is a unique identifier of each tuple in the table. A primary key can be a single attribute or a combination of attributes.
  • Tables can be related to each other by using foreign keys, which are attributes that refer to the primary key of another table. A foreign key establishes a relationship between two tables, such as one-to-one, one-to-many, or many-to-many.
  • The schema of a relational database is the set of table names, attributes, domains, and constraints that define the structure and integrity of the database.

SQL

SQL is the standard language for interacting with relational databases. SQL allows users to perform various operations on relational databases, such as:

  • Creating, altering, and dropping tables and other database objects
  • Inserting, updating, and deleting data in tables
  • Selecting and retrieving data from tables using various criteria and operators
  • Joining and combining data from multiple tables using different types of joins, such as inner join, outer join, cross join, etc.
  • Grouping and aggregating data using functions such as sum, count, average, etc.
  • Sorting and ordering data using the order by clause
  • Applying conditions and filters using the where and having clauses
  • Creating and using views, indexes, triggers, stored procedures, and other database objects
  • Granting and revoking permissions and roles to users and groups

SQL is a declarative language, which means that users specify what they want to do with the data, not how to do it. The RDBMS is responsible for translating the SQL statements into low-level commands and executing them on the database.

Advantages of Relational Databases

Relational databases have several advantages over other types of databases, such as:

  • Accuracy: Relational databases ensure that the data is consistent and valid by enforcing integrity constraints, such as primary keys, foreign keys, unique keys, not null, check, etc. These constraints prevent the insertion of duplicate, incomplete, or incorrect data into the database.
  • Ease of use: Relational databases are easy to use and understand because they use a simple and intuitive data model based on tables and relationships. Users can access and manipulate the data using SQL, which is a widely used and standardized language.
  • Collaboration: Relational databases allow multiple users to access and share the data concurrently and securely. The RDBMS handles the concurrency control and transaction management to ensure that the data is isolated and consistent among different users. The RDBMS also provides authentication and authorization mechanisms to control the access and privileges of different users and groups.
  • Security: Relational databases protect the data from unauthorized access, modification, or deletion by using encryption, backup, and recovery techniques. The RDBMS also supports auditing and logging features to track and monitor the activities and changes on the database.
  • Categorization: Relational databases allow users to organize and classify the data into different categories and levels of abstraction by using schemas, views, subqueries, and other database objects. These objects help users to simplify and customize the access and presentation of the data according to their needs and preferences.

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