The SQL CREATE VIEW statement is a very powerful feature in RDBMSs that allows users to create virtual tables based on the result set of a SQL query. Unlike regular tables, these views do not store data themselves rather they provide a way of dynamically retrieving and presenting data from one or many underlying tables. Views help simplify complex queries, enhance security by controlling access to specific data, and provide an easy way for data abstraction and encapsulation.
This article explains how the SQL CREATE VIEW statement can be used to create, modify, and drop views, along with their pros and cons. It also provides practical examples of how database management can involve customized report generation, enforcing access control, and simplifying complex structures. Learning how to use views effectively can significantly enhance your database management skills, whether you’re a beginner or an experienced database developer seeking to improve search query performance.
SQL CREATE VIEW Statement
The SQL CREATE VIEW statement is the central idea used to create a virtual table that does not store data itself but rather provides a dynamic representation of data obtained from one or more underlying tables. This arrangement lets users simplify intricate queries, improve security, and make abstracted data structures easy to access and manipulate.
Syntax:
The syntax to create a view in sql is as follows:
CREATE VIEW view_name AS
SELECT column1, column2, …
FROM table_name
WHERE condition;
Explanation of Syntax:
- CREATE VIEW view_name: This part of the statement specifies that a new view with the given name (view_name) will be created.
- AS: This keyword is used to indicate that the following SELECT statement will define the structure and data for the view.
- SELECT column1, column2, …: Here, you specify the columns that you want the view to include. These can be columns from one or more tables or even expressions derived from those columns.
- FROM table_name: This part of the statement specifies the table or tables whose data will populate your view.
- WHERE condition: Optionally you may add a WHERE clause so as to give conditions under which data retrieved by this view should be filtered by. This is very helpful when creating views with subsets of data.
Examples of SQL CREATE VIEW Statement
Example 1: Creating a Simple View
Consider the table products having three columns product_id, product_name, and price. Suppose we have to create a view that contains only products whose prices are greater than $50.
CREATE VIEW employee_department_info AS
SELECT e.employee_id, e.first_name, e.last_name, d.department_name
FROM employees e
JOIN departments d ON e.department_id = d.department_id;
Assuming the products table contains the following data:
products table
The expensive_products view will contain:
expensive_products
Explanation:
- We develop a view called expensive_products.
- The view obtains columns product_id, product_name, and price from table products.
- We filter it so that it only includes rows with prices bigger than $50.
Now, if we query the expensive_products view, we will only see products with prices above $50.
Example 2: Creating a Joined View
Assume that we have two tables employees and departments. We need to build a view combining information about both tables in order to show each employee’s name along with their department name:
CREATE VIEW employee_department_info AS
SELECT e.employee_id, e.first_name, e.last_name, d.department_name
FROM employees e
JOIN departments d ON e.department_id = d.department_id;
Employees table:
employees table
Departments table:
departments table
The output of the employee_department_info view would be:
Output of the employee_department_info view
Explanation:
- A view named employee_department_info is created by us.
- Columns employee_id, first_name, last_name from employees table along with department_name from departments table are selected by this view.
- An inner join between employees and departments on department_id is performed to get department name for each employee.
Now when querying the employee_department_info view we shall have a list of employees together with their corresponding department names.
Conclusion
In conclusion, the SQL CREATE VIEW statement is a useful resource for those in database development and administration because it creates virtual tables that provide simplified access to data stored in one or more underlying tables. The views encapsulate complex queries, control data access, and abstract the data structures enhancing the performance of Database Management Systems (DBMS), security, and manageability.
Therefore, by using views properly developers can avoid writing unnecessary code enhance query execution time, and finally make sure that their databases have a higher level of security when processing errors appear. View mastering is important in improving efficiency and effectiveness during database management tasks regardless of whether you are operating small-scale applications or significant enterprise databases.