查看此SQL语句，选择三个正确答案确认可以使查询成功执行的ORDER BY子句（ABD） SELECT cust_id, cust_last_name "Last Name" FROM customers WHERE country_id = 10 UNION SELECT cust_id CUST_NO, cust_last_name FROM customers WHERE country_id = 30; A、ORDER BY 2, 1 B、ORDER BY "Last Name" C、ORDER BY "CUST_NO" D、ORDER BY 2,cust_id E、ORDER BY CUST_NO 解析： drop table customers; create table customers(cust_id int,country_id int,cust_last_name varchar(20)); insert into customers values(1,10,'Oracle'); insert into customers values(2,30,'MySQL'); commit; SQL> SELECT cust_id, cust_last_name "Last Name" 2 FROM customers 3 WHERE country_id = 10 4 UNION 5 SELECT cust_id CUST_NO, cust_last_name 6 FROM customers 7 WHERE country_id = 30; CUST_ID Last Name ---------- -------------------- 1 Oracle 2 MySQL