sql - 标量子查询包含多于一行

Question

我正在使用 H2 数据库并想移动一些数据。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

我想通过我的查询实现什么:

其实每 CUSTOMER有一个 CUSTOMER_SERVICE .我只想移动 COLUMN EMAIL来自 CUSTOMER_SERVICE到 CUSTOMER table 。为此，我已经向用户添加了一个电子邮件列。我希望能够通过我的查询来做到这一点，但显然不是。

Answer 1

您的选择查询返回不止一行。如果您不想这样做，那么您需要执行聚合或 LIMIT 1 之类的操作或类似操作。