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View of Data in DBMS : Limitations and Challenges of Data Views

Views in a Database Management System (DBMS) provide the end-user with different ways of looking at data that are simpler or formatted differently. These views also assist in presenting pictures of intricate databases and provide security against information breaches. It is always important to understand the concept of data views for the database management and security of the data.

We shall investigate the importance of these views and their use in DBMS, as well as the ensuring types that they are available and their operationalisation within this blog. We will also share their benefits, disadvantages, and efficient management guidelines.

The Importance of Data Views in DBMS

Data views play a crucial role in how users interact with and manage data within a Database Management System (DBMS). They provide a way to present data that is tailored to specific needs, making complex data structures more accessible and secure. In this section, we’ll explore the key aspects that highlight the importance of data views in DBMS.

Understanding Data Abstraction

Data abstraction involves hiding all the database complexity from the user and presenting only just enough information.

• Ease of User interaction: Views abstract complex data structures by providing users with adequate relevant data.
• Focus on Relevant Data: Simplifying the data means that users do not have to care about the physical layout of data storage.
• Improved Data Protection: Because of the view, people do not have access to view sensitive information, thereby blocking other unauthorised users from seeing it.

Data abstraction in DBMS is essential because it allows users to interact with the data without being overwhelmed by its complexity. Through views, users can access a simplified version of the data that meets their specific needs. This means that they only see what is necessary for their tasks, without being exposed to the entire database structure. Additionally, data abstraction through views enhances security by controlling what data is accessible to different users.

Role of Data Views in Data Security

Data views are instrumental in enforcing security policies within a DBMS. They act as a protective layer that controls user access to data.

• Controlled Data Access: Views restrict access to specific data, ensuring that users only see what they are permitted to view.
• Limited Exposure To Information: Views enable users to access information only that is necessary by concealing parts of it.
• Protection of Sensitive Data: Administrators can limit information on unauthorised persons by creating views which do not contain the restricted details.

Data views in DBMS are critical aspects of the security of any database. By the use of views, a database administrator is able to create different versions of one database so that each individual or group is shown only the appropriate information. This means that sensitive elements will only be shown to persons who have a need to know, which improves the security of the database significantly.

Simplifying Complex Queries with Views

Views can simplify complex queries, making it easier for users to interact with the database without needing to write intricate SQL commands.

• Predefined Query Logic: Views store complex queries that can be reused, saving time and reducing errors.
• User-Friendly Access: Users can retrieve data through a simple SELECT statement on a view, without needing to understand the complex query logic behind it.
• Consistent Data Retrieval: Views ensure that the same logic is applied consistently across different queries, leading to more reliable results.

Working with databases often requires writing complex SQL queries to retrieve or manipulate data. Views simplify this process by allowing administrators to define complex queries once and store them as a view. Users can then access the data through this view using straightforward SELECT statements, without needing to understand the intricate logic behind the scenes. This not only makes the database more user-friendly but also ensures consistency in how data is retrieved across the organisation.

Types of Data Views in DBMS

In a DBMS, data views can be categorised into three main types:

• Logical Views
• Physical Views
• External Views

Each of these types serves a different purpose and is designed to meet specific needs within the database environment. Below is an explanation of each type:

Logical Views

Logical views are user-centric, focusing on how data is presented to users rather than how it is stored. These views abstract the complexity of the database, making it easier for users to interact with the data.

• User-Centric Approach: Logical views are designed to align with how users think about data, providing a simplified perspective that doesn’t reveal the underlying database schema.
• Data Abstraction: By abstracting the complexity, logical views allow users to focus on the relevant information without worrying about the intricate details of data storage.
• Combination of Data: Logical views can pull together data from multiple tables, presenting it in a unified and meaningful way, which is particularly useful for complex queries.

Physical Views

Physical views are concerned with how data is actually stored within the database. These views are primarily used for optimising performance and managing the physical storage of data.

• Storage Optimization: Physical views help in organising data storage efficiently, ensuring that the DBMS can quickly retrieve the required data.
• Performance Enhancement: It is possible to customise data access paths in advance therefore performance is improved with the use of physical views, which increases the speed with which the database performs.
• Efficient Data Management: Such views physically allow administrators to allocate the storage resources in a manner that preserves the performance of the whole system.

External Views

External views are customised to meet the specific needs of different users or applications. They provide a unique perspective of the data and can be customised so as to ensure that users get only information that is necessary to them.

• Customised Data Access: When providing data access control using external views, each user or external application’s view is created to fit the particular requirements of such a user or application, thereby presenting information in a way that a user can understand.
• Security and Privacy: External views also provide protection since they limit the users from viewing certain data and therefore sensitive data is kept from unauthorised users.
• Simplified Interaction: There are external views that enable users to operate the database more conveniently by providing the part of the data to be used and hiding irrelevant data.

How Data Views Work in DBMS

Now, let’s understand how views work in SQL with examples. We’ll start by creating two tables, then use these tables to demonstrate how to create, update, and delete views in a database.

Example Tables

Let’s consider two tables: Employees and Departments. These tables will store information about employees and the departments they belong to.

Employees Table:

Departments Table:

SQL Queries to Create and Insert Data into Tables:

Creating a View in SQL

A view in SQL is a virtual table that contains a subset of data from one or more tables. It does not store data physically but provides a way to access and display data from the tables it references.

Example:

Let’s create a view called EmployeeDetails that shows the employee’s full name, department name, and salary.

Explanation:

The CREATE VIEW statement creates a new view named EmployeeDetails.

The SELECT statement inside the view combines the Employees and Departments tables using an INNER JOIN based on DepartmentID.

The FullName column concatenates FirstName and LastName to provide the full name of the employee.

The view displays the full name, department name, and salary of each employee.

While views themselves do not store data, they can be updated in some cases. However, not all views are updatable, especially if they involve complex queries like joins or aggregations.

Example:

Let’s assume we need to update the EmployeeDetails view to include the employee’s EmployeeID.

Explanation:

The CREATE OR REPLACE VIEW statement is used to modify an existing view. The updated view now includes the EmployeeID along with the full name, department name, and salary.

Also Read: UPDATE Query in SQL

Deleting a View in SQL

If a view is no longer needed, it can be removed from the database.

Example:

Explanation:

The DROP VIEW statement is used to delete the EmployeeDetails view from the database.

After executing this command, the view will no longer exist, but the underlying tables (Employees and Departments) will remain unaffected.

Limitations and Challenges of Data Views

Although views in DBMS offer many advantages, they come with certain limitations and challenges that need to be considered during implementation.

• Performance Overhead: Views can slow down query performance, especially when they are based on complex queries involving multiple tables.
• Maintenance Complexity: As the database evolves, keeping views up-to-date can become difficult, especially in dynamic environments.
• Restricted Updates: Not all views are updatable, particularly those with joins, aggregations, or complex calculations.
• Dependency on Underlying Tables: If the structure of the underlying tables changes, the views need to be manually adjusted, leading to potential maintenance issues.

Also Read: Natural Join in SQL

Best Practices for Managing Data Views

To make the most of views and avoid common pitfalls, certain best practices should be followed when managing data views in a DBMS.

• Keep Views Simple: Avoid overly complex queries in views to maintain good performance and ease of use.
• Use Indexing: Apply indexes on columns frequently used in views to optimise query performance.
• Limit View Dependencies: Minimise dependencies between views and underlying tables to reduce maintenance issues.
• Regular Audits: Periodically review views to ensure they remain relevant and efficient as database structures change.
• Security Considerations: Use views to restrict access to sensitive data by exposing only the necessary columns and rows.

Also Read: Hierarchical Model in DBMS

Conclusion

According to this blog post, views in DBMS are very useful in enhancing data access, maintaining security and improving efficiency. The end users do not have to deal with the complicated structure for long because fewer complicated queries are called for the required data. By abstracting the real data, views help users as they provide a virtual environment and eliminate the need to think about the complexities of the data.

Nonetheless, it is important to have an understanding of the scope of using views as well as the likely problems involved. There must be some control over the implementation and regular feedback in order for views to provide real benefits to the organisation. For that reason, steps should be taken in order to counter the adverse impact of the use of views and thus enhance organisational performance.