You can use the UPDATE statement to change the column values of existing rows.

For example, the following example shows how to offer anyone who is a manager a 10% raise:

    SELECT ename, sal FROM emp WHERE job = 'MANAGER';

 ename |   sal
-------+---------
 JONES | 2975.00
 BLAKE | 2850.00
 CLARK | 2450.00
(3 rows)

UPDATE emp SET sal = sal * 1.1 WHERE job = 'MANAGER';

SELECT ename, sal FROM emp WHERE job = 'MANAGER';

 ename |   sal
-------+---------
 JONES | 3272.50
 BLAKE | 3135.00
 CLARK | 2695.00
(3 rows)