請告訴我如何爲這樣一個問題

Question

創建更新查詢我有兩個表：

1. 
CREATE TABLE [dbo].[HotelSourceMap](
[hotelsourcemapid] [bigint] IDENTITY(1,1) NOT NULL, 
[dspartnerid] [bigint] NOT NULL, 
[dshotelid] [bigint] NOT NULL, 
[countrycode] [varchar](5) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, 
[countryid] [bigint] NULL) 

2. 
CREATE TABLE [dbo].[country](
[countryId] [smallint] IDENTITY(1,1) NOT NULL, 
[countryName] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, 
[countryCode] [varchar](2) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL) 

的情況是這樣的： 我想從country.countryid更新HotelSourceMap表countryid。 其中hotelsourcemap.countrycode = country.countrycode

一些事情是這樣的：

UPDATE HotelSourceMap 
SET 
HotelSourceMap.countryid =country.countryId 
WHERE 
HotelSourceMap.countrycode = country.countryCode 

Answer 1

有可能就是這個基於集合的解決方案，在這種情況下，這將是最好的，我敢肯定有人會它張貼，但在那之前，至少這將做的工作：

UPDATE 
    HotelSourceMap 
SET 
    countryid = (SELECT countryId FROM country WHERE country.countryCode = HotelSourceMap.countrycode) 

Answer 2

這實在是值得商榷表的設計，但這裏是SQL：

UPDATE HotelSourceMap 
SET  countryid = co.countryId 
FROM  HotelSourceMap AS hsm 
    JOIN country  AS co 
     ON (hsm.countryCode = co.countryCode)