一、

The employee table contains these columns.

LAST_NAME VARCHAR2(25) FIRST_NAME VARCHAR2(25) DEPT_ID

NUMBER(9)

You need to display the names of the employees that are not assigned to the

department. Evaluate this SQL statement.

SELECT last_name, first_name

FROM employee

WHERE dept_id is NULL

Which change should you make to achieve the desired result?

A. Create an outer join.

B. Change the column in the where condition.

C. Change the operator in the where condition

D. Add a second condition to the where condition

TK上答案C，我觉得所有答案都不对。这个语句可以实现它所要做的功能

二、

Which statement about multiple sub-queries is True?

A. A pair wise comparison produces a cross product.

B. A non-pair wise comparison produces a cross product.

C. In a pair wise subquery, the values returned from the subquery are compared

individually to the values in the outer query.

D. In a non-pair wise subquery, the values returned from the subquery are

compared as a group to the values in the outer query.

请大家对这道题分析一下，

三、

Evaluate the SQL statement.

SELECT e.id, (.15* e.salary) + (.25* e.bonus),

(s.sale_amount * (.15* e.commision_pct))

FROM employee e , sales

WHERE e.id = s.emp_id;

What would happen if you removed all the parenthesis from calculation?

A. Results will be lower.

B. Results will be higher.

C. Statement will not execute.

D. Statement will achieve some results.

TK上答案是C，我觉得所有答案都不对。去掉括号，仍能执行

四、

When selecting data which statement is valid about projection?

A. Projection allows due to choose rows.

B. Projection allows due to choose columns.

C. Projection allows due to joined tables together.

D. Projection allows due to add columns to a table.

Answer: B

请问什么为projection?

请大家一起讨论,不甚感激