Why do we create view in database? What are its types? Describe with example. What is Authorization control in DDB?

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Creating views in a database serves several important purposes, and they can be categorized into different types based on their functionality and use cases. Additionally, authorization control in distributed databases (DDB) is crucial for ensuring data security and integrity. Below, I will discuss the reasons for creating views, their types with examples, and the concept of authorization control in DDB.

Reasons for Creating Views in a Database

  1. Simplification of Complex Queries: Views can encapsulate complex SQL queries, making it easier for users to access data without needing to understand the underlying complexity.
  2. Data Abstraction: Views provide a way to present data in a specific format or structure without exposing the underlying tables. This abstraction can help in hiding sensitive data.
  3. Security: By using views, database administrators can restrict access to specific rows or columns of data. Users can be granted access to a view without having direct access to the underlying tables. Views can restrict access to certain columns or rows of a table. By creating a view, you can grant users access to only the specific data they need, hiding sensitive information from them.
  4. Data Consistency: Views can present a consistent representation of data, even if the underlying tables change. This is particularly useful in scenarios where data is frequently updated. A view ensures that data is consistently presented. If the database structure changes, the view can be updated without affecting the users. Users continue to query the same view, and the system ensures that they get the correct data.
  5. Aggregation and Calculation: Views can be used to perform calculations or aggregations on data, providing summarized information without altering the original data.
  6. Reusability: Views can be reused across multiple queries. By storing a commonly used query as a view, developers can reduce redundancy and ensure consistency in data retrieval.

Types of Views

  1. Simple Views: These are based on a single table and do not contain any functions or groupings. They can be used to simplify access to specific columns of a table. Example:
   CREATE VIEW EmployeeNames AS
   SELECT FirstName, LastName FROM Employees;

In this example, the view EmployeeNames provides a simplified way to access the first and last names of employees without exposing other details.

  1. Complex Views: These are based on multiple tables and can include joins, aggregations, and functions. Example:
   CREATE VIEW DepartmentSalary AS
   SELECT d.DepartmentName, AVG(e.Salary) AS AverageSalary
   FROM Departments d
   JOIN Employees e ON d.DepartmentID = e.DepartmentID
   GROUP BY d.DepartmentName;

Here, the view DepartmentSalary provides the average salary for each department by joining the Departments and Employees tables.

  1. Materialized Views: Unlike regular views, materialized views store the result set of the query physically. They can improve performance for complex queries but require maintenance to keep the data up to date. Example:
   CREATE MATERIALIZED VIEW SalesSummary AS
   SELECT ProductID, SUM(Quantity) AS TotalSold
   FROM Sales
   GROUP BY ProductID;

This materialized view SalesSummary stores the total quantity sold for each product, which can be queried quickly without recalculating the totals each time.

Authorization Control in Distributed Databases (DDB)

Authorization control in DDB refers to the mechanisms and policies that govern who can access and manipulate data within the distributed database system. It is essential for maintaining data security, privacy, and integrity. Key aspects of authorization control include:

  1. User Authentication: Ensuring that users are who they claim to be, typically through usernames and passwords, tokens, or other authentication methods.
  2. Access Control: Defining what actions users can perform on the database. This can include:
  • Read Access: Allowing users to view data.
  • Write Access: Allowing users to insert, update, or delete data.
  • Execute Access: Allowing users to execute stored procedures or functions.
  1. Role-Based Access Control (RBAC): Users are assigned roles that define their permissions. For example, a user with the “Manager” role may have access to sensitive financial data, while a user with the “Employee” role may only have access to their own records.
  2. Granular Permissions: Authorization can be applied at various levels, such as:
  • Table Level: Permissions can be set for entire tables.
  • Row Level: Permissions can be set for specific rows based on user attributes.
  • Column Level: Permissions can be set for specific columns, allowing sensitive information to be hidden.
  1. Audit and Monitoring: Keeping track of who accessed what data and when, which is crucial for compliance and security audits.

In summary, views in databases serve to simplify data access, enhance security, and provide abstraction. They can be categorized into simple, complex, and materialized views, each serving different purposes. Authorization control in distributed databases is vital for ensuring that only authorized users can access or manipulate data, thereby maintaining the security and integrity of the database system.

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