VIEW 定义中基础表的含义是什么

发布于 2024-10-02 17:40:06 字数 350 浏览 2 评论 0原文

我不明白，

VIEW定义中底层表的含义是什么，

A view is created by joining one or more tables. When you update record(s) in a view, it updates the records in the underlying tables that make up the view.

So, yes, you can update the data in a view providing you have the proper privileges to the underlying tables.

原文

am not understand ,

what is the meaning of underlying table in VIEW definition ,

A view is created by joining one or more tables. When you update record(s) in a view, it updates the records in the underlying tables that make up the view.

So, yes, you can update the data in a view providing you have the proper privileges to the underlying tables.

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且行且努力 2024-10-09 17:40:06

将视图视为存储的查询，它对用户来说就像一个常规表。实际上，视图

SELECT somefield, otherfield
FROM theview

与数据库级别实际发生的情况

SELECT somefield, otherfield
FROM (
   SELECT lots, of, useless,fields, somefield, otherfield
   FROM underlying, tables
   JOIN ...
) AS theview

之间几乎没有什么区别：视图使您不必每次都编写子查询，因此在这方面它们可以节省时间。但是，视图有一个缺点，即根据基础查询，您可能无法像直接访问基础表那样对视图运行 UPDATE/DELETE 查询。

Think of a view as a stored query, which appears to the user as a regular table. In practical terms, there's very little difference between a view:

SELECT somefield, otherfield
FROM theview

and what's actually happening at the database level:

SELECT somefield, otherfield
FROM (
   SELECT lots, of, useless,fields, somefield, otherfield
   FROM underlying, tables
   JOIN ...
) AS theview

Views save you from having to write the sub-query each time, so they're a time saver in that regard. However, views have the downside that depending on the underlying query, you might not able to run UPDATE/DELETE queries against the view as you could if you were directly accessing the underlying tables.

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