Views

A view is a virtual table based on a SQL query. This chapter introduces how to create and use views.

Create View

-- Basic view
CREATE VIEW active_users AS
SELECT id, name, email
FROM users
WHERE status = 'active';

-- Query view
SELECT * FROM active_users;

View with JOIN

-- View with multiple tables
CREATE VIEW user_orders AS
SELECT 
    u.id,
    u.name,
    o.order_number,
    o.total_amount
FROM users u
JOIN orders o ON u.id = o.user_id;

Replace View

-- Replace existing view
CREATE OR REPLACE VIEW active_users AS
SELECT id, name, email, city
FROM users
WHERE status = 'active';

Drop View

-- Drop view
DROP VIEW IF EXISTS active_users;

View Advantages

1. Simplify complex queries
2. Security - hide sensitive columns
3. Reusability
4. Data abstraction

View Limitations

1. Performance overhead
2. Cannot always update
3. Depends on base tables

Summary

• CREATE VIEW: Create view
• DROP VIEW: Delete view
• Views simplify queries
• Use for security and abstraction

Next Step: Learn INDEXES