Oracle timestamp data type

Question

what is the different between timestamp data type without parameter and with parameter 0:

timestamp VS timestamp(0)

Answer 1

The number in parentheses specifies the precision of fractional seconds to be stored. So, (0) would mean don't store any fraction of a second, and use only whole seconds. The default value if unspecified is 6 digits after the decimal separator.

So an unspecified value would store a date like:

TIMESTAMP 24-JAN-2012 08.00.05.993847 AM

And specifying (0) stores only:

TIMESTAMP(0) 24-JAN-2012 08.00.05 AM

See Oracle documentation on data types.