OCP-1Z0-051 第41題 視圖的注意事項

一、原題

Which two statements are true regarding views? (Choose two.)

A. A subquery that defines a view cannot include the GROUP BY clause.

B. A view that is created with the subquery having the DISTINCT keyword can be updated.

C. A view that is created with the subquery having the pseudo column ROWNUM keyword cannot be updated.

D. A data manipulation language ( DML) operation can be performed on a view that is created with the subquery having all the NOT NULL columns of a table.

答案：CD

二、題目翻譯

關于視圖的描述哪兩句話是正确的？（選擇兩個）

A. 定義視圖的子查詢不能包含GROUP BY子句。

B. 包含DISTINCT關鍵字的子查詢建立的視圖可以被更新。

C. 包含ROWNUM關鍵字僞列的子查詢建立的視圖不能被更新。

D. 包含表中所有非空列的子查詢建立的視圖可以執行DML操作。

三、題目解析

A選項不正确，視圖可以包含GROUP BY子句，但包含了group by 子句的視圖，不能進行DML操作。

B選項不正确，視圖可以包含DISTINCT關鍵字，但包含DISTINCT關鍵字的視圖不能被更新。

C選項正确，rownum是僞列，使用者無法更新。

D選項正确。