Question

我正在使用H2数据库，想要移动一些数据。为此我创建了以下查询：

UPDATE CUSTOMER
SET EMAIL = SELECT service.EMAIL
FROM CUSTOMER_SERVICE AS service
INNER JOIN CUSTOMER AS customer ON service.ID = customer.CUSTOMER_SERVICE_ID;

当我现在在H2控制台中执行它时，我收到以下错误：

Scalar subquery contains more than one row; SQL statement:

UPDATE CUSTOMER
SET EMAIL = SELECT service.EMAIL
FROM CUSTOMER_SERVICE AS service
INNER JOIN CUSTOMER AS customer ON service.ID = customer.CUSTOMER_SERVICE_ID [90053-192] 90053/90053 (Hilfe)

这个错误告诉我什么？

编辑

我希望通过查询实现目标：

实际上每个CUSTOMER都有一个CUSTOMER_SERVICE。我只是想将COLUMN EMAIL从CUSTOMER_SERVICE移到CUSTOMER表。为此，我已经向用户添加了一个电子邮件列。我希望能够用我的查询来做，但显然不是。

Answer 1

您的查询在语法上无效（所有子查询都必须在它们周围括号）。

您缺少的是相关条款。我相信你想要：

UPDATE CUSTOMER c
    SET EMAIL = (SELECT cs.EMAIL
                 FROM CUSTOMER_SERVICE s
                 WHERE s.ID = c.CUSTOMER_SERVICE_ID
                );

我不知道这应该是什么：[90053-192] 90053/90053 (Hilfe)。

Answer 2

您的至少一位客户的子查询有多个电子邮件地址。

你可以... (Select top 1 serverice.email ... 或... (Select max(serverice.email) ...

Update Customer Set EMail=B.Email
 From  Customer A
 Join  (Select ID,max(EMail) as EMail From CUSTOMER_SERVICE Group By ID) B
   on  (A.CUSTOMER_SERVICE_ID = B.ID)

Answer 3

您的选择查询返回多行。如果你不想要它，那么你需要做一些像聚合或LIMIT 1或类似的东西。

标量子查询包含多行

3 个答案: