Question

我正在将数据从一个表转移到另一个表。

旧表曾经有一个名为City的varchar列。

新表（而不是城市名称）具有一个名为CityId的int列，因为我仅为城市创建了新表。

“我的城市”表具有以下列：

CityID - PK

RegionID - FK

CityName - Varchar(50)

我正在运行此查询以复制新表的旧数据：

INSERT INTO dbo.Client(EmailAddress, CityID)
a.EmailAddress, (SELECT CityID FROM Cities WHERE CityName collate SQL_Latin1_General_CP1_CI_AS = a.City)
FROM AdventureWorksOld.dbo.Client a

但是我不能这样做，因为子查询返回多行：

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

如何修复我的代码，以便可以执行以下操作：

SELECT (SELECT CityName FROM Cities WHERE CityName = 'Oak Bay') -> Replace 'Oak Bay' with the text in the column
FROM AdventureWorksOld.dbo.Client

谢谢。

Answer 1

这可能是您在寻找什么？

INSERT INTO dbo.Client(EmailAddress, CityID)
SELECT 
    a.EmailAddress
,   c.CityID 
FROM AdventureWorksOld.dbo.Client a
LEFT JOIN Cities c ON c.CityName = a.City

Answer 2

尝试一下：

INSERT INTO dbo.Client(EmailAddress, CityID)
SELECT 
    a.EmailAddress
,   c.CityID 
FROM AdventureWorksOld.dbo.Client a
OUTER APPLY (SELECT TOP 1 c.CityID FROM Cities c WHERE c.CityName = a.City) c

问题从旧表迁移到新表

2 个答案: