MYSQL JOIN 出现 AND 错误

Question

我试图从 Names 表中提取 first_name，但前提是该 users_id 位于 Orders 表中并且 order_num = 1，但我不断收到错误。

SELECT first_name
FROM customers
LEFT JOIN orders
ON orders.order_id = customers.cust_id 
AND orders.order_num = 1

但我的查询返回多个值，而不是仅一个值，就像它忽略 orders.order_num=1 - 我的查询看起来正确吗，还是我做错了什么？

Answer 1

SELECT first_name
FROM customers
LEFT JOIN orders
ON orders.order_id = customers.cust_id 
WHERE orders.order_num = 1