Question

我有两张桌子

用户：phone_number，优惠券

客户：customer_id，优惠券

我想创建一个帮助表，根据特定的优惠券将用户和customer_id链接在一起。第三个表将有三个字段：coupon，phone_number，customer_id，应该从这两个表中检索。我尝试了内部加入，但似乎不起作用。有人可以帮忙吗？

SELECT customers.customer_id as customer_id, users.phone as 
phone
FROM linked_customers_users 
INNER JOIN customers
ON linked_customers_users.customer_id = customers.customer_id
INNER JOIN users
ON linked_customers_users.phone = users.phone

Answer 1

尝试LEFT JOIN：

SELECT customers.customer_id as customer_id, users.phone as 
phone
FROM linked_customers_users 
LEFT JOIN customers
ON linked_customers_users.customer_id = customers.customer_id
LEFT JOIN users
ON linked_customers_users.phone = users.phone

Answer 2

道歉作为评论者指出你正在使用mysql。您可以随时尝试模拟完整的外部联接（请注意，如果您拥有它们，将删除重复项）：

SELECT * FROM linked_customers_users 
LEFT JOIN users ON linked_customers_users.coupon = users.coupon
UNION
SELECT * FROM linked_customers_users 
RIGHT JOIN users ON linked_customers_users.coupon = users.coupon

根据关系将两个表连接在一个辅助表中

2 个答案: