select
to_timestamp(SCHEDULED_TIME,'YYYY-MM-DD HH24:MI:SS.FF') as SCHEDULED_TIME,
TRUNC(to_date(to_timestamp(SCHEDULED_TIME,'YYYY-MM-DD HH24:MI:SS.FF'),'YYYY-MM-DD HH24:MI:SS'))
from S_TIDAL_STATUS
The error was: ORA-01830: date format picture ends before converting entire input string 01830. 00000 - "date format picture ends before converting entire input string"
The goal is to return something like
2017-07-91 23:14:00 (without the content after the dot).
The problem in your attempt is the function TO_DATE() applied to a timestamp. TO_DATE() takes a VARCHAR2 (string) input, not a timestamp. So Oracle converts the timestamp to a string first, implicitly, using your NLS_TIMESTAMP_FORMAT parameter, and then attempts to convert this string to a date. Depending on your NLS_TIMESTAMP_FORMAT, you may get different errors.
The way to convert a timestamp to a date (datetime) - while truncating off the fractions of a second - is with the CAST function. Example:
select systimestamp,
cast (systimestamp as date) as ts_cast_to_date
from dual
;
Alternatively, if all your strings are EXACTLY in that format, you can truncate the strings first and apply TO_DATE directly:
to_date(substr(scheduled_time, 1, 19), 'yyyy-mm-dd hh24:mi:ss')