SQL - Use Views for Simplified and Reusable Queries

Views are virtual tables created by defining a query in your database. They allow you to simplify complex queries, enhance data security, and promote code reusability. Here's how you can benefit from using views:

• Simplify Complex Queries: Instead of writing long and complex SQL queries whenever you need specific data, create a view that encapsulates the query logic. This makes your SQL code more concise and easier to read.

   -- Create a view to simplify the query for retrieving product sales
   CREATE VIEW ProductSales AS
   SELECT
       p.product_id,
       p.product_name,
       SUM(o.quantity * o.unit_price) AS total_sales
   FROM
       products p
       JOIN order_details o ON p.product_id = o.product_id
   GROUP BY
       p.product_id, p.product_name;

   -- Now, you can query the view to get product sales
   SELECT * FROM ProductSales;

• Enhance Data Security: Views can restrict access to certain columns or rows, providing an additional layer of security. Users can interact with the view without having direct access to the underlying tables.

   -- Create a view with restricted columns for sensitive data
   CREATE VIEW EmployeesSensitive AS
   SELECT employee_id, first_name, last_name
   FROM employees;

   -- Grant access to the view instead of the underlying table
   GRANT SELECT ON EmployeesSensitive TO some_user;

• Code Reusability: Views can be reused in multiple queries or incorporated into other views. This promotes code reusability and consistency across your SQL codebase.

   -- Create a view based on the ProductSales view
   CREATE VIEW TopSellingProducts AS
   SELECT *
   FROM ProductSales
   WHERE total_sales > 10000;

   -- Reuse the TopSellingProducts view in various reports and queries
   SELECT * FROM TopSellingProducts;

• Performance Optimization: In some cases, views can improve performance by precomputing complex calculations or aggregations, allowing you to query the view instead of repeating those operations in multiple places.

When using views, remember that they are virtual representations of data, and the underlying data may change. Ensure that your views are up to date and accurately reflect the data you intend to query. Additionally, use views judiciously and avoid creating overly complex or deeply nested views, as they can make your database schema harder to maintain and understand.