Github user JasonWHowell commented on the pull request:
https://github.com/apache/spark/pull/7847#issuecomment-133617010
Thanks for the hard work here.
Did this land in documentation yet? I searched for it at
https://spark.apache.org/docs/latest/sql-programming-guide.html but didn't find
any reference yet.
Someone is asking if there is a way to extract different granularities of
the time unit from Spark SQL DateDiff(). Such as milliseconds vs. days vs.
months. I suppose we could with simple division if the DateDiff returns
milliseconds units, and divide by 1000 and 60 and 60 up to hours units and
again by 24 up to days units.
If we only return days units in the difference, the result would be rounded
(losing hours and seconds precision) so multiplying x24x60x60 to get seconds is
going to be extremely lossy.
I think folks are used to the SQL Server implementation of DateDiff (where
you provide the DatePart unit), as opposed to the Hive DateDiff and MySQL
implementation which seems to return only rounded day parts.
https://msdn.microsoft.com/en-us/library/ms189794.aspx
Appreciate any advice, or point me to the right forum. Sorry to bother ~
Jason
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