Key Difference Between View and Table

In database management systems (DBMS), understanding the difference between view and table is crucial for efficient database design and querying. Both views and tables are essential components, but they serve different purposes and operate differently. While a table is a physical structure storing data, a view is a virtual representation of data derived from tables.

This article provides a comprehensive comparison of views and tables, highlighting their features, advantages, and use cases.

What is a Table in DBMS?

A table is a fundamental building block of a database. It is a physical structure that stores data in rows (records) and columns (fields). Each table has a schema defining its structure, including column names, data types, and constraints.

Features of a Table:

1. Physical Storage: Data is stored directly in the table.
2. Primary Key: Ensures uniqueness of each record.
3. Indexes: Improve data retrieval speed.
4. Permanent: Exists until explicitly deleted.

Example of a Table:

Employee Table:

EmployeeID	Name	Department	Salary
101	John Doe	HR	50000
102	Jane Doe	IT	60000

What is a View in DBMS?

A view is a virtual table representing the result of a query. It does not store data physically but retrieves it from one or more underlying tables whenever queried. Views simplify complex queries and enhance security by controlling access to specific data.

Features of a View:

1. Virtual Representation: Contains no physical data.
2. Dynamic Updates: Reflects changes in the underlying tables.
3. Simplifies Queries: Encapsulates complex SQL queries.
4. Security Control: Restricts user access to specific columns or rows.

Example of a View:

HighSalaryEmployees View:

CREATE VIEW HighSalaryEmployees AS  
SELECT Name, Department, Salary  
FROM Employee  
WHERE Salary > 55000;

Querying the view:

Name	Department	Salary
Jane Doe	IT	60000

Key Differences Between View and Table

Aspect	Table	View
Definition	Physical structure storing data.	Virtual representation of a query.
Storage	Stores data physically.	Does not store data physically.
Data Update	Data can be added, modified, deleted.	Reflects changes in underlying tables.
Speed	Faster as it stores data directly.	Slower due to query execution.
Security	Requires explicit constraints.	Can restrict access to specific data.
Dependency	Independent.	Depends on underlying tables.
Persistence	Exists permanently until deleted.	Exists as long as its query is valid.

Advantages of Using Tables

1. Data Integrity:
   Ensures consistency with primary keys, foreign keys, and constraints.
2. High Performance:
   Direct access to data makes operations faster.
3. Versatility:
   Stores structured data for diverse applications.
4. Relational Framework:
   Enables relationships between different entities in the database.

Advantages of Using Views

1. Simplified Queries:
   Complex SQL logic is encapsulated in a single view.
2. Enhanced Security:
   Limits user access to sensitive data by displaying only specific columns or rows.
3. Dynamic Updates:
   Reflects real-time changes in the underlying tables.
4. Logical Independence:
   Shields users from schema changes in underlying tables.

Practical Applications

When to Use Tables

1. Data Storage:
   Tables are essential for storing persistent data.
2. Relationships:
   Used to define primary and foreign keys.
3. Indexes:
   Improves query performance through indexing.

When to Use Views

1. Data Security:
   Limit user access to sensitive columns like Salary.
2. Reporting:
   Generate simplified reports with pre-defined SQL logic.
3. Data Abstraction:
   Hide complexity of underlying tables from end-users.

FAQs: Difference Between View and Table

1. What is the main difference between a view and a table?

A table physically stores data, while a view is a virtual table generated by querying one or more tables.

2. Can data be updated in a view?

Yes, but only if the view is based on a single table and does not include aggregated or computed columns.

3. Why are views slower than tables?

Views execute their underlying query each time they are accessed, whereas tables provide direct data access.

4. Can a view exist without a table?

No, a view depends on one or more tables for its data.

5. How do views enhance database security?

Views restrict access to specific columns or rows, allowing controlled data visibility for users.