为什么我可以用SCHEMABINDING修改视图引用的表?

问题描述

正在寻找关于SCHEMABINDING的一些说明.我在一个论坛中读到，如果您使用Schemabinding创建视图，则不能更改基表.

Looking for some clarification on SCHEMABINDING. I read in a forum that if you create a view with Schemabinding, the base table cannot be altered.

因此，我使用SCHEMABINDING创建了一个视图，并能够从基表中删除一列.

So I created a view with SCHEMABINDING and was able to drop a column from the base table.

因此，现在我对SCHEMABINDING的目的以及何时何地使用SCHEMABINDING感到困惑.

So, now I am confused on what is the purpose of SCHEMABINDING and when and where should this be used?

注意:由于SCHEMABINDING，我试图删除基表，但无法这样做.

NOTE: I tried to drop the base table and I was not able to do so because of SCHEMABINDING.

推荐答案

SCHEMABINDING不仅限于对象级绑定.在这种情况下，实际上可能只绑定到特定的列.举一个非常简单的例子:

SCHEMABINDING is not restricted to just object-level bindings. In this case, it is actually possible to only be bound to specific columns. Take this very trivial example:

CREATE TABLE dbo.foo(a INT, b INT);
GO

CREATE VIEW dbo.vFoo
WITH SCHEMABINDING
AS
  SELECT a FROM dbo.foo;
GO

由于该视图仅引用列a，因此我可以放下b没问题:

Since the view only references column a, I can drop b no problem:

ALTER TABLE dbo.foo DROP COLUMN b;
GO

但是，一旦我尝试触摸a，就会出现问题:

But as soon as I try to touch a, problem:

ALTER TABLE dbo.foo DROP COLUMN a;
GO

错误:

因此，无论谁写了他们在该论坛上写的东西，他们都不是很明确或详尽. 文档会有所帮助，但是您仍然需要推断:

So, whoever wrote what they wrote in that forum, they weren't very explicit or elaborate. The documentation is a little more helpful, but you still need to extrapolate:

请注意，该句子在单词修饰"之后并未结束.删除视图中未引用的列不会以影响视图定义的方式修改表，因为它不知道未引用的列.

Notice the sentence does not end after the word "modified." Dropping a column that isn't referenced in the view is not modifying the table in a way that would affect the view definition, because it does not know about a column it doesn't reference.

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