请教一个ocp的测试题，实在没看懂，哪位有空解答一下，谢谢:)

licheer

The employee table contains these columns:
FIRST-NAME VARCHER2(25)
COMISSION NUMBER(3,2)

Evaluate this SQL statement

SELECT first-name,commission
FROM employee
WHERE commission=
(SELECTcomission
FROM employee
WHERE UPPER(first-name)= ‘scott’)

Which statement will cause this statement to fail?

A. Scott has a null commission resolution.
B. Scott has a zero commission resolution.
C. There is no employee with the first name Scott.
D. The first name values in the data base are in the lower case.

这个语句只是没有数据返回
怎么会报错呢？

ora_teacher

子查询返回的值是null,
因为 commission = null 是错误的,
should be
commission is null

imtj

选择A

topsec007

a right

8509345

题目中的 'scott' 应该是大写吧

licheer

做了这样的测试数据：
create table employee (first_name varchar2(20),commission number(10));

insert into employee values ('a',null);
insert into employee values ('b',1);
insert into employee values ('c',1);
insert into employee values ('d',1);
insert into employee values ('scott',1);
insert into employee values ('scott',null);
insert into employee values ('scott',2);

commit;
SELECT first_name,commission
FROM employee
WHERE commission=
(SELECT commission
FROM employee
WHERE UPPER(first_name)= 'scott');

结果没有报错阿

blue_stone

a没有得到想要的结果，从语法上来说，并没有错。
我觉得可能出错的情况就是: 表中有两个或多个记录first name 都是scott