Updatable Join Views【每日一译】--20121202

A join view is defined as a view that has more than one table or view in its FROM
clause (a join) and that does not use any of these clauses: DISTINCT, aggregation,
GROUP BY, START WITH, CONNECT BY, ROWNUM, and set operations (UNION ALL,

INTERSECT, and so on).

一个联接视图的定义是它拥有大于一个表或视图在它的FROM语句（联接）并且不能使用任何

这些语句：DISTINCT,聚合，GROUP BY,START WITH,CONNECT BY,ROWNUM,和集合操作

（UNION ALL,INTERSECT等）。

An updatable join view is a join view that involves two or more base tables or views,
where UPDATE, INSERT, and DELETE operations are permitted. The data dictionary
views ALL_UPDATABLE_COLUMNS, DBA_UPDATABLE_COLUMNS, and USER_
UPDATABLE_COLUMNS contain information that indicates which of the view columns
are updatable. In order to be inherently updatable, a view cannot contain any of the

following constructs

一个可更新的联接视图是它引用两个或者更多的基表或视图，在此视里UPDATE,INSERT,和

DELETE操作是被允许的。数据字典视图ALL_UPDATABLE_COLUMNS,DBA_UPDATABLE_COLUMNS

和USER_UPDATABLE_COLUMNS包含显示视图中可被更新列的信息。为了可以内在的可更新，一个视

图不能包含任何以下的结构:

■ A set operator
■ A DISTINCT operator
■ An aggregate or analytic function
■ A GROUP BY, ORDER BY, CONNECT BY, or START WITH clause
■ A collection expression in a SELECT list
■ A subquery in a SELECT list
■ Joins (with some exceptions)
Views that are not updatable can be modified using INSTEAD OF triggers

不可更新的视图可以通过INSTEAD OF触发器修改