问题：

[多选]

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?（）

A . deleting the records of employees who do not earn commission
B . increasing the commission of employee 3 by the average commission earned in department 20
C . finding the number of employees who do NOT earn commission and are working for department 20
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 . decreasing the commission by 150 for the employees who are working in department 30 and earning a commission of more than 800