Converts a duration to the selected field and appends the value as a long or double column. Valid fields are hours, minutes, seconds, nano-, micro- and milliseconds. If the output should be a long value the conversion result will be truncated, e.g. if the duration 1 hour 30 minutes should be converted to hours, the exact output is 1.5 hours whereas the truncated output 1 hour.

Note: Only time-based durations can be converted to numbers, since the conversion of date-based durations is not well defined (e.g. it is not clearly defined how many days a month has).