Rows can be removed from a table using the DELETE
    command.
    Suppose you are no longer interested in the weather of Hayward.
    Then you can do the following to delete those rows from the table:
DELETE FROM weather WHERE city = 'Hayward';
All weather records belonging to Hayward are removed.
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
(2 rows)
One should be wary of statements of the form
DELETE FROM tablename;
    Without a qualification, DELETE will
    remove  all  rows from the given table, leaving it
    empty.  The system will not request confirmation before
    doing this!