Assume pts is a PERIOD(TIMESTAMP(2)) column in table t with a value of PERIOD '(2005-02-03 12:12:12.34, 2005-02-03 12:12:12.35)'.
In the following example, column pts is cast as TIMESTAMP(6). The result is the source beginning bound with trailing zeros added to the fractional seconds to make the precision 6.
SELECT CAST(pts AS TIMESTAMP(6)) FROM t;
The following is returned: