Question

如果无法在不加入联接的情况下编写以下代码，我会遇到麻烦吗？如果可能的话，有人可以帮助解释和编写没有它的代码吗？

SELECT DISTINCT CONCAT(first_name, ' ', last_name) AS customer_name,
 state AS customer_state
FROM customers c JOIN addresses a
 ON c.customer_id = a.customer_id
ORDER BY last_name, first_name

Answer 1

您在这里：

SELECT DISTINCT 
  CONCAT(c.first_name, ' ', c.last_name) AS customer_name,
  (SELECT a.state FROM addresses a WHERE a.customer_id=c.customer_id ) AS customer_state
FROM customers c 
ORDER BY c.last_name, c.first_name

是否可以使用子查询但不使用JOIN编写以下查询？

1 个答案: