2. 计算机
  3. Exhibit: UPDATE EzonexamConsolidated SET District = ‘Mexico’ WHERE RtvID = 45 You work as database administrator at Ezonexam.co

Exhibit: UPDATE EzonexamConsolidated SET District = ‘Mexico’ WHERE RtvID = 45 You work as database administrator at Ezonexam.co

admin2009-05-19  48
问题 Exhibit:
UPDATE EzonexamConsolidated
SET District = ‘Mexico’
WHERE RtvID = 45

You work as database administrator at Ezonexam.com. You handle one SQL Server 2000 computer and one database.
When users run the query in the exhibit above the receive the following error message:
Server: Mrh3612, Level 16, Stats 1, Line 1
View or function ‘EzonexamConsolidated’ is not updateable because it
contains aggregates:

How should you enable the query to run?
选项 A、Create a non-normalized EzonexamConsolidated table and populate the table with data from the base tables.
B、The appropriate users should be granted UPDATE permissions on each base table.
C、To enable updates on the composite tables create an INSTEAD OF trigger on the view.
D、On each base table add a cascading update trigger.
答案C
解析 Explanation: SQL Server 2000 uses INSTEAD OF triggers and partitioned views to enhance the class of updateable views. INSTEAD OF triggers can be created on a view in order to make a view updateable. The INSTEAD OF trigger is executed instead of the data modification statement on which the trigger is defined. This trigger allows the user to specify the set of actions that need to take place in order to process the data modification statement. Thus, if an INSTEAD OF trigger exists for a view on a given data modification statement, the corresponding view is updateable through that statement. If the view is a partitioned view, the view is updateable, subject to certain restrictions.

Incorrect Answers:
A: Creating a table that combines the composite tables that the view is based on would deny us the ability to use the view to return aggregated column values.

B: The error message is not related to permissions but to the updateable of the table.

D: Cascading referential integrity constraints makes it possible to define the actions SQL Server 2000 takes when a user attempts to delete or update a key to which existing foreign keys point. Cascading referential integrity constraints fire AFTER triggers after all of the cascading referential actions directly caused by the original DELETE or UPDATE are performed.
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