Question

我一直收到错误代码＃1241。我一直在寻找答案，但我无法找到帮助我的答案。

这是我的代码：

SELECT name, address, city, phone  
FROM customer
WHERE customer.ID IN (
    SELECT customer.ID, COUNT(*) AS amount_reservations 
    FROM customer, (
        SELECT ID 
        FROM customer, reservations 
        WHERE rent_time = 'weekend' AND 
        ID = customer_ID
    ) AS foo 
    WHERE customer.ID = foo.ID 
    GROUP BY customer.ID 
    HAVING amount_reservations > 1
)

Answer 1

子查询SELECT customer.ID, COUNT(*) AS amount_reservations应该有一个SINGLE列，而不是两列。

将其更改为：

SELECT name, address, city, phone  
  FROM customer  
  WHERE customer.ID IN (
    SELECT customer.ID
      FROM customer, (
        SELECT ID FROM customer, reservations 
          WHERE rent_time = 'weekend' AND ID = customer_ID
        ) AS foo 
      WHERE customer.ID = foo.ID 
      GROUP BY customer.ID HAVING count(*) > 1
    )

Answer 2

我强烈建议您重写查询。删除子查询 - 不需要它们。然后使用explicit joins代替逗号。

select c.id, c.name, c.address, c.city, c.phone  
from customer c
    join reservations r on c.id = r.customer_id
where r.rent_time = 'weekend'
group by c.id, c.name, c.address, c.city, c.phone  
having count(*) > 1

Answer 3

如果您想使用in，您可以从根本上简化查询：

SELECT c.name, c.address, c.city, c.phone  
FROM customer c
WHERE c.ID IN (SELECT r.customer_id
               FROM reservations r
               WHERE r.rent_time = 'weekend' 
               GROUP BY r.customer_id
               HAVING COUNT(*) > 1
              ) ;

注意：

从不在FROM子句中使用逗号。始终使用正确，明确，标准的JOIN语法。
对所有列引用使用表别名和限定列名。
您在子查询中不需要JOIN，因为您在预订表中有客户ID。

错误＃1241 SQL查询

3 个答案: