大數據就業實戰培訓 Oracle就業實戰培訓
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071考試-第4題、choose the best answer
View the Exhibits and examine PRODUCTS and SALES tables.
You issue the following query to display product name and the number of times the
product has been sold:
SQL>SELECT p.prod_name, i.item_cnt
FROM (SELECT prod id, COUNT(*) item_cnt
FROM sales GROUP BY prod_id) i RIGHT OUTER JOIN products p
ON i.prod_id = p.prod_id;
What happens when the above statement is executed?
A) The statement executes successfully and produces the required output.
B) The statement produces an error because a subquery in the FROM clause and outer-joins cannot be used together.
C) The statement produces an error because ITEM_CNT cannot be displayed in the outer query.
D) The statement produces an error because the GROUP BY clause cannot be used in a subquery in the FROM clause.
Answer：A
(SQL> select d.dname,e.emp_cnt
from (select deptno,count(*) emp_cnt from emp group by deptno)e right outer join dept d
on e.deptno=d.deptno;
DNAME EMP_CNT
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ACCOUNTING 2
RESEARCH 4
SALES 6
OPERATIONS
TRAIN)
