difference between two timestamps

[nimo frey]

I have two timestamps in my database-table:

start:

 2010-09-01 08:00:00.000000

and

stop:

2010-09-01 12:00:00.000000

and want the difference in seconds by a query:

select stop-start from table

does not work as it returns

40000.000000.

And I have no clue what it means.

Any suggestions?