The UPDATE command is used to modify attribute values of one or more selected tuples.As in delete command, a WHERE clause in the UPDATE command selects the tuples to be modified from a single relation.

For example to changethe major of student 123456789 to CIS:

UPDATE     student
SET              major = 'cis'
WHERE      stuid = '123456789';

This sets the major of the student with an id 123456789 as cis.As shown above, more WHERE conditionals, using AND, must be used to limit the updating to more specific rows. Also,
additional columns may be set by separating equal statements with commas.

UPDATE     faculty
SET             dept = 'cis'
                 rank = 'assistant'
WHERE      facname = 'annber';

This updatesseveral fields in a record-change  ANNBER to  CIS DEPT and assistant
          
      
UPDATE   class
SET            room = 'F110'
WHERE    facid =
(SELECT   facid
FROM        faculty
WHERE     facname = 'annber') ;

This  query specifically uses a subquery for updation. It changes the room to F110 forall of
 ANNBER'S courses