[GENERAL] How to drop a NOT NULL column constraint?

[Ed Loehr]

I have a table created like so:

        CREATE TABLE foo (
                id INTEGER NOT NULL
                ...
        );

I need to alter the table to get rid of the "NOT NULL" constraint on the
'id' column.  Can I do this using ALTER TABLE?  Or do I have to
dump/recreate/reload the table?  

I'm looking for something like "ALTER TABLE foo ALTER COLUMN id DROP NOT
NULL", but the docs don't hint at it...

Regards,
Ed Loehr