Anjali writes the following commands with respect to a table employee having fields, empno, name, department, commission :

Command1: Select count(*) from employee;
Command2: Select count(commission) from employee;

She gets the output as 4 for the first command but gets an output 3 for the second command. Explain the output with justification.

What is the use of ORDER BY clause ?

Write an example query that sorts on three columns.

Write a query that sorts the data of table student on the basis of Project-Group (in ascending order), section (in descending order), Marks (in descending order).