## 2.8. Updates

You can update existing rows using the `UPDATE` command. Suppose you discover the temperature readings are all off by 2 degrees after November 28. You can correct the data as follows:

    UPDATE weather
        SET temp_hi = temp_hi - 2,  temp_lo = temp_lo - 2
        WHERE date > '1994-11-28';

Look at the new state of the data:

    SELECT * FROM weather;

         city      | temp_lo | temp_hi | prcp |    date
    ---------------+---------+---------+------+------------
     San Francisco |      46 |      50 | 0.25 | 1994-11-27
     San Francisco |      41 |      55 |    0 | 1994-11-29
     Hayward       |      35 |      52 |      | 1994-11-29
    (3 rows)