milliseconds requires systimestamp, and ss is seconds no matter how many times you repeat it in a string...it's a format mask. you mean to use something like FF2, FF3, FF6 or maybe FF9.
to_char(systimestamp, 'HH24:MI:SS.FF3') FROM dual; is going to get rounded unless you are using the new datetime2 datatypes in SQL 2008+
16:18:53.124 for example, will not transalate 100% as the minimim milliseconds must end in 0,3 or 7 as mentioned before.
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