Which three tasks would require subqueries or joins in order to be performed in a single step?

Click the Exhibit button and examine the data from the EMP table.

The COMMISSION column shows the monthly commission earned by the employee.
Which three tasks would require subqueries or joins in order to be performed in a single step?
(Choose three.)

A.
finding the number of employees who do NOT earn commission and are working for
department 20

B.
increasing the commission of employee 3 by the average commission earned in department 20

C.
decreasing the commission by 150 for the employees who are working in department 30 and
earning a commission of more than 800

D.
inserting into the table a new employee 10 who works for department 20 and earns a
commission that is equal to the commission earned by employee 3

E.
creating a table called COMMISSION that has the same structure and data as the columns
EMP_ID and COMMISSION of the EMP table

F.
deleting the records of employees who do not earn commission

Explanation:

Increasing the commission of employee 3 by the average commission earned in department 20
will require sub-queries or joins in order to perform in a single step . Inserting into the table a new
employee 10 who works for department 20 and earns a commission that is equal to the
commission earned by employee 3 is correct answer also. To create a table that has the same
structure as subset of columns from another table it’s required to use a subquery in order to
perform in a single step.
Incorrect Answers:
A: This query can be done without using sub-queries or joins in order to perform in a single step.
C: It is not required to use sub-queries or joins to create SQL statement for that query.
F: This query can be done without using sub-queries or joins in order to perform in a single step:
only two conditions in the WHERE clause should be specified.