Relational Operators

There are six Relational Operators in SQL, and after introducing them, we'll see how they're used: 
 =          Equal
 
 !=             Not Equal 
 <              Less Than
 >              Greater Than
 <=            Less Than or Equal To
 >=            Greater Than or Equal To 


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. 

SELECT   stuname, stuid
FROM       student
WHERE    credits < 
(SELECT    AVG (credits)
FROM         student)
gives you the names and  ID'S of all studentswho have less than the  AVERAGE  number of
CREDITS of all students in the database.