#视图

-- 基本视图
CREATE VIEW active_users AS
SELECT id, name, email
FROM users
WHERE status = 'active';

-- 查询视图
SELECT * FROM active_users;

-- 多表视图
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;

-- 替换现有视图
CREATE OR REPLACE VIEW active_users AS
SELECT id, name, email, city
FROM users
WHERE status = 'active';

-- 删除视图
DROP VIEW IF EXISTS active_users;