使用两个表中的数据，但不需要连接？

SELECT order_id, (SELECT customer_name FROM customers WHERE customers.customer_id = orders.customer_id) AS customer_name
FROM orders;

# 假设使用Python和SQLite
import sqlite3

conn = sqlite3.connect('example.db')
cursor = conn.cursor()

# 查询orders表
cursor.execute("SELECT order_id, customer_id FROM orders")
orders = cursor.fetchall()

# 查询customers表
cursor.execute("SELECT customer_id, customer_name FROM customers")
customers = {row[0]: row[1] for row in cursor.fetchall()}

# 合并结果
for order in orders:
    order_id, customer_id = order
    customer_name = customers.get(customer_id, "Unknown")
    print(f"Order ID: {order_id}, Customer Name: {customer_name}")

conn.close()

CREATE VIEW order_customer_view AS
SELECT orders.order_id, customers.customer_name
FROM orders, customers
WHERE orders.customer_id = customers.customer_id;

SELECT * FROM order_customer_view;

CREATE TEMPORARY TABLE temp_orders AS
SELECT orders.order_id, customers.customer_name
FROM orders, customers
WHERE orders.customer_id = customers.customer_id;

SELECT * FROM temp_orders;

SELECT order_id, 'orders' AS table_name FROM orders
UNION ALL
SELECT customer_id, 'customers' AS table_name FROM customers;