Compound Conditions / Logical Operators :
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)

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

AND & OR can be combined

An easier method of using compound conditions uses IN or BETWEEN

SELECT     stuid, stuname
FROM         student
WHERE      credits =
             ( SELECT    MAX (credits)
               FROM        student)
Finds the  STUID AND STUNAME WITH THE MAXIMUM NUMBER OF CREDITS.