Best way to define Timestamp column?

[Max Ten]

CREATE TABLE t (
  ts1 TIMESTAMP ,
  ts2 TIMESTAMP NOT NULL DEFAULT '0000-00-00 00:00:00' 
);

INSERT INTO T (TS2) VALUES ('0001-01-01-00.00.00.000000');

If execute the insert statement, ts1 column can be blank, but ts2 must have a valid datetime value.

So by using getTimestamp in java to retrieve from Derby,  what is the pro and cons when creating timestamp column as above?

 

thank you.