oe@OCM> select * from ord_vu;
ORDER_ID ORDER_DATE NO OF ITEMS
---------- --------------------------------------------------------------------------- -----------
2354 15-JUL-08 08.18.23.234567 AM 13
2361 14-NOV-07 05.34.21.986210 AM 9
2363 24-OCT-07 07.49.56.346122 AM 9
2367 28-JUN-08 11.53.32.335522 AM 8
省略结果。。。。。。。。。。。。。。。
三、答案C是错的，在创建视图时，对这种使用各种函数，或运算表达式的列，一定要起别名，如没有别名视图创建就会失败，操作如下：
[html]
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 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)
3 GROUP BY o.order_id,o.order_date;
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)
*
ERROR at line 2:
ORA-00998: must name this expression with a column alias
把上面的视图改成如下：
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 AS SELECT o.order_id,o.order_date,COUNT(i.line_item_id) CT FROM orders o JOIN order_items i ON(o.order_id=i.order_id)
3 GROUP BY o.order_id,o.order_date;
View created.
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 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)
3 GROUP BY o.order_id,o.order_date;
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)
*
ERROR at line 2:
ORA-00998: must name this expression with a column alias
把上面的视图改成如下：
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 AS SELECT o.order_id,o.order_date,COUNT(i.line_item_id) CT FROM orders o JOIN order_items i ON(o.order_id=i.order_id)
3 GROUP BY o.order_id,o.order_date;
View created.
四、答案D也是错的，错误与答案C一个问题
[html]
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 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)
3 GROUP BY o.order_id,o.order_date
4 WITH CHECK OPTION;
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)
*
ERROR at line 2:
ORA-00998: must name this expression with a column alias
把上面的视图改成如下：
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 AS SELECT o.order_id,o.order_date,COUNT(i.line_item_id)||'NO OF ITEMS' CT FROM orders o JOIN order_items i ON(o.order_id=i.order_id)
3 GROUP BY o.order_id,o.order_date
4 WITH CHECK OPTION;
View created.
oe@OCM> CREATE OR REPLACE VIEW ord_vu
2 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)
3 GROUP BY o.order_id,o.order_date
4 WITH CHECK OPTION;
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)
*
ERROR at line 2:
ORA-00998: must n