Working with MySQL Views: Alternative Approaches to Using Subqueries in the FROM Clause

CREATE VIEW recent_orders AS
  SELECT *
  FROM orders
  WHERE order_date > (SELECT MAX(order_date) - INTERVAL 7 DAY FROM orders);

This view attempts to create a view named recent_orders that selects all orders placed within the last 7 days. However, the subquery within the FROM clause (finding the maximum order date and subtracting 7 days) is not allowed.

There are several reasons behind this restriction:

• Complexity: Subqueries within the FROM clause can make views harder to understand and maintain, especially for complex queries.
• Optimization Challenges: The MySQL optimizer might have difficulties efficiently processing views with subqueries in the FROM clause.
• Performance Concerns: Repeated executions of the subquery within the view can potentially impact performance.

While you cannot directly use subqueries in the FROM clause, there are alternative approaches to achieve similar results: