Question

我有一个Update查询，其中from表与其中一个连接表相同。它看起来像这样

Update Contacts
Set NewContactId = repCt.Id
From Contacts ct
Join Contacts repCt on repCt.ClientId = ct.ClientId
                       AND <a bunch of other join criteria>
Where <a bunch of other criteria hitting both ct and repCt>

当我运行此命令时，我会发出一条错误，指出The table 'Contacts' is ambiguous，这意味着我无法在Update查询中包含两次相同的表。那么我应该如何进行此更新（或者有解决方法）？

Answer 1

Update ct --use the alias defined in from
Set NewContactId = repCt.Id
From Contacts ct
Join Contacts repCt on ct.ClientId = repCt.ClientId
                       AND <a bunch of other join criteria>
Where <a bunch of other criteria hitting both ct and repCt>

Answer 2

您也可以使用以下查询

MERGE INTO Contacts ct
USING Contacts repCt
ON (ct.ClientId = ct.ClientId
AND <a bunch of other join criteria>)
WHEN MATCHED THEN
SET NewContactId = repCt.Id
WHERE <a bunch of other criteria hitting both ct and repCt>;

更新时尝试使用MERGE函数而不是加入

Answer 3

我能够通过将查询的整个from...join部分放入一个嵌套的子查询中来解决这个问题，然后将其加入。所以最终结果如下：

Update Contacts
Set NewContactId = t.newId
From Contacts ct
Join (
    select ct.Id, r.Id
    from contacts ct
    join contacts r on ct.clientid = r.clientid
    <all of the joins>
) as t on ct.Id

更新具有相同From和Join表的查询报告不明确的表错误

3 个答案: