18th October 2018: PostgreSQL 11 Released!
Unsupported versions: 6.4

Updates

You can update existing instances using the update command. Suppose you discover the temperature readings are all off by 2 degrees as of Nov 28, you may update the data as follow:

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