MySQL - UPDATE multiple rows with different values in one query

You can do it this way:

UPDATE table_users
    SET cod_user = (case when user_role = 'student' then '622057'
                         when user_role = 'assistant' then '2913659'
                         when user_role = 'admin' then '6160230'
                    end),
        date = '12082014'
    WHERE user_role in ('student', 'assistant', 'admin') AND
          cod_office = '17389551';

I don't understand your date format. Dates should be stored in the database using native date and time types.

MySQL allows a more readable way to combine multiple updates into a single query. This seems to better fit the scenario you describe, is much easier to read, and avoids those difficult-to-untangle multiple conditions.

INSERT INTO table_users (cod_user, date, user_rol, cod_office)
VALUES
('622057', '12082014', 'student', '17389551'),
('2913659', '12082014', 'assistant','17389551'),
('6160230', '12082014', 'admin', '17389551')
ON DUPLICATE KEY UPDATE
 cod_user=VALUES(cod_user), date=VALUES(date)

This assumes that the user_rol, cod_office combination is a primary key. If only one of these is the primary key, then add the other field to the UPDATE list. If neither of them is a primary key (that seems unlikely) then this approach will always create new records - probably not what is wanted.

However, this approach makes prepared statements easier to build and more concise.

You can use a CASE statement to handle multiple if/then scenarios:

UPDATE table_to_update 
SET  cod_user= CASE WHEN user_rol = 'student' THEN '622057'
                   WHEN user_rol = 'assistant' THEN '2913659'
                   WHEN user_rol = 'admin' THEN '6160230'
               END
    ,date = '12082014'
WHERE user_rol IN ('student','assistant','admin')
  AND cod_office = '17389551';