The WHERE clause is used to specify that only certain rows of the table are displayed, based on the criteria described in that WHERE clause. It is most easily
understood by looking at a couple of examples. 

If you wanted to see the EMPLOYEEIDNO's of those making at or over $50,000, use the following: 

SELECT EMPLOYEEIDNO 
FROM EMPLOYEESTATISTICSTABLE 
WHERE SALARY >= 50000; 

Notice that the >= (greater than or equal to) sign is used, as we wanted to see those who made greater than $50,000, or equal to $50,000, listed together. This
displays:

The AND operator joins two or more conditions, and displays a row only if that row's data satisfies ALL conditions listed (i.e. all conditions hold true). For
example, to display all staff making over $40,000, use: 

SELECT EMPLOYEEIDNO 
FROM EMPLOYEESTATISTICSTABLE 
WHERE SALARY > 40000 AND POSITION = 'Staff';

The OR operator joins two or more conditions, but returns a row if ANY of the conditions listed hold true.

To see all those who make less than $40,000 or have less
than $10,000 in benefits, listed together, use the following query: 

SELECT EMPLOYEEIDNO 
FROM EMPLOYEESTATISTICSTABLE 
WHERE SALARY < 40000 OR BENEFITS < 10000;