Fractional Second precision in DBMSs

Question

I would like to know what Fractional Second Precision is, with some examples.
And how different DBMSs support it?

Answer 1

sql-server Sql Server 2008 and newer has DATETIME2 which is has precision of 100ns

Character length 19 positions minimum (YYYY-MM-DD hh:mm:ss ) to 27 maximum (YYYY-MM-DD hh:mm:ss.0000000)

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Precision, scale 0 to 7 digits, with an accuracy of 100ns. The default precision is 7 digits.

http://msdn.microsoft.com/en-us/library/bb677335.aspx

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mysql - MySQL 5.6.4

MySQL 5.6.4 and up expands fractional seconds support for TIME, DATETIME, and TIMESTAMP values, with up to microseconds (6 digits) precision:

http://dev.mysql.com/doc/refman/5.6/en/fractional-seconds.html