18. View the Exhibit and examine the data in ORDERS and ORDER_ITEMS tables. You need to create a view that displays the ORDER ID, ORDER_DATE, and the total number of items in each order. Which CREATE VIEW statement would create the view successfully?
A. CREATE OR REPLACE VIEW ord_vu (order_id,order_date) AS SELECT o.order_id, o.order_date, COUNT(i.line_item_id) "NO OF ITEMS" FROM orders o JOIN order_items i ON (o.order_id = i.order_id) GROUP BY o.order_id,o.order_date
B. CREATE OR REPLACE VIEW ord_vu AS SELECT o.order_id, o.order_date, COUNT(i.line_item_id) "NO OF ITEMS" FROM orders o JOIN order_items i ON (o.order_id = i.order_id) GROUP BY o.order_id,o.order_date
C. CREATE OR REPLACE VIEW ord_vu AS SELECT o.order_id, o.order_date, COUNT(i.line_item_id) FROM orders o JOIN order_items i ON (o.order_id = i.order_id) GROUP BY o.order_id,o.order_date
D. CREATE OR REPLACE VIEW ord_vu AS SELECT o.order_id, o.order_date, COUNT(i.line_item_id)||' NO OF ITEMS' FROM orders o JOIN order_items i ON (o.order_id = i.order_id) GROUP BY o.order_id,o.order_date WITH CHECK OPTION
答案: B
分析: 本題考點是視圖/view
建立視圖的指令格式為:
create or replace view view_name as (select...from...)
A. 視圖的列名是通過select語句指定的。
C. 沒有為COUNT(i.line_item_id)列取别名,别人檢視視圖時無法了解該列的含義。
D. ||用來連接配接2個字元串