mysql - 没有公共(public)键的 SQL 连接查询

Question

我有这个获取客户列表的查询

SELECT CONCAT(first_name, ' ', last_name) as customer_name, customer_email as customer_email FROM customers WHERE user_level = 'customer')

对于每一行我都想追加这个查询

(SELECT CONCAT(first_name, ' ', last_name) as seller_name, seller_email FROM users WHERE user_level = 'seller')

对于每个客户，卖家都是一样的，因为我的表中只有一个卖家，所以我想得到这个输出。我该如何创建它？

customer_name    |     customer_email    |    seller_name    |     Seller_email
-------------------------------------------------------------------------------
some customer    |   xxxxxxxxxxx         |    this seller    |    seller@email.com
some customer1   |   xxxxxxxxxxx         |    this seller    |    seller@email.com
some customer2   |   xxxxxxxxxxx         |    this seller    |    seller@email.com

Answer 1

因为您的users 表中只有一条记录，您可以使用cross join 来获得您想要的结果；

SELECT CONCAT(c.first_name, ' ', c.last_name) as customer_name, 
       c.customer_email as customer_email,
       CONCAT(u.first_name, ' ', u.last_name) as seller_name, 
       u.seller_email 
FROM customers c cross join users u
WHERE c.user_level = 'customer'
      and u.user_level = 'seller'