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Database Views

Introduction

What are Database Views?

Database views are virtual tables that provide a specific representation of data from one or more tables in a database. Unlike physical tables, views do not store data themselves; instead, they display data stored in other tables. This allows for a simplified and focused access to complex datasets.

They simplify complex queries, presenting users with a more manageable data structure, and can enhance data security by restricting access to specific columns or rows.

Creating Views

Creating a Database View in SQL

Creating a database view in SQL involves defining a virtual table based on the result set of a SELECT query. This allows users to simplify complex queries and enhance data accessibility. Views can represent a subset of data or aggregate information from multiple tables.

To create a view, the SQL statement ‘CREATE VIEW’ is used followed by the view name and the SELECT statement defining the view’s contents. Understanding how to effectively create and manage views can significantly streamline database interactions.

Advantages

Advantages of Database Views

Improving Data Security

In sensitive environments, views restrict user access to certain data without exposing the complete database. This allows organizations to comply with privacy regulations while allowing users to perform necessary functions.

Simplifying Complex Queries

By encapsulating complex joins and calculations, views make it easier for users to interact with data. This is particularly useful in reporting and analytics, where users can retrieve necessary insights without deep database knowledge.

Drawbacks

Drawbacks of Database Views

Database views can introduce additional overhead, especially if they involve complex queries or join operations. This can lead to slower response times if not managed properly.

Example

Example Database View

Suppose we have two tables: employees and departments.

Employees Table

employee_id first_name last_name department_id salary
1 John Doe 101 50000
2 Jane Smith 102 60000
3 Jim Brown 101 45000
4 Emily Davis 103 70000

Departments Table

department_id department_name
101 HR
102 IT
103 Finance

SQL

SQL to create the view

We want to create a view that shows the employee’s full name and the department they work in, with the salary information.

SQL to create the view:

CREATE VIEW employee_department_view AS
SELECT e.first_name || ' ' || e.last_name AS full_name,
e.salary,
d.department_name
FROM employees e
JOIN departments d ON e.department_id = d.department_id;

Resuls

Result of the View

The view will provide a combined result from the employees and departments tables.

full_name salary department_name
John Doe 50000 HR
Jane Smith 60000 IT
Jim Brown 45000 HR
Emily Davis 70000 Finance

How it works:

 

  • The view employee_department_view combines data from the employees table and the departments table.
  • You can query the view like a regular table: SELECT * FROM employee_department_view;
  • This simplifies the query and abstracts the complexity of joining the tables each time.