当匹配的行存在于另一个表中时更新行 [英] UPDATE row when matching row exists in another table

问题描述

仅当另一个表中存在匹配的行时，我才需要将表上的字段更新为真，对于主表中该列当前为空的所有行.

I need to update a field on a table to be true only if a matching row exists in another table, for all the rows where the column is currently null in the main table.

这是对我想要实现的目标的描述:

This is a description of what I want to achieve:

UPDATE [LenqReloaded].[dbo].[Enquiry] A 
SET [ResponseLetterSent] = 1
WHERE [ResponseLetterSent] IS NULL
   AND EXISTS
       (
           SELECT * FROM [LenqReloaded].[dbo].[Attachment] B 
           WHERE A.[EnquiryID] = B.[EnquiryID]
       )

这在语法上不正确.

我无法通过 IF EXISTS... 语句对其进行编码，因为我没有 [EnquiryID] 没有从表中读取数据.

I can't code it via an IF EXISTS... statement because I don't have the [EnquiryID] without reading the data from the table.

我应该如何格式化我的 UPDATE 语句?

How should I format my UPDATE statement?

推荐答案

离你不远了...

UPDATE A
SET A.[ResponseLetterSent] = 1 
FROM [LenqReloaded].[dbo].[Enquiry] A
WHERE A.[ResponseLetterSent] IS NULL 
    AND EXISTS ( SELECT * FROM [LenqReloaded].[dbo].[Attachment] B WHERE A.[EnquiryID] = B.[EnquiryID] )

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