Subject | RE: [IBO] info on database design |
---|---|
Author | Kaputnik |
Post date | 2001-11-15T22:43:37Z |
Most of the questions already answered, but I would like to add my 2cents to
the date-issue
A Datetime is nothing more than a Double (in Delphi) which means it is 64
Bits large. In Interbase/FB I think it is pretty similar. The Problem is
only, that parts of it are reserved for the fraction (the time of day) so
you will have less bits available for the date-part of it (the whole numbers
are the days that passed from 1.1.1899, the fraction is the time of the
day).
A Generator in Interbase is a pure 64 Bit Integer, so you will always have
more generator-values available than dates are available.
Ah, 64 Bits are somewhat a very large number (Exactly
18.446.744.073.709.551.616). To store a table with only two columns (the PK
and the Date) you would need (naively calculated) 16 bytes per row and
therefore 274.877.906.944 GB (millions of Terrabyte!!) onto your harddrive
would require several hundreds of Terrabytes before you reach the end of the
generator. Don't you think that this is enough?
Nick Josipovic
CRM Administration
BIT-Institute
Prof. Dr. Franz Steffens
Schloss
68163 Mannheim
Germany
Phone: ++49 621 181-1621
Fax: ++49 621 181-1618
mailto:nick.josipovic@...
the date-issue
A Datetime is nothing more than a Double (in Delphi) which means it is 64
Bits large. In Interbase/FB I think it is pretty similar. The Problem is
only, that parts of it are reserved for the fraction (the time of day) so
you will have less bits available for the date-part of it (the whole numbers
are the days that passed from 1.1.1899, the fraction is the time of the
day).
A Generator in Interbase is a pure 64 Bit Integer, so you will always have
more generator-values available than dates are available.
Ah, 64 Bits are somewhat a very large number (Exactly
18.446.744.073.709.551.616). To store a table with only two columns (the PK
and the Date) you would need (naively calculated) 16 bytes per row and
therefore 274.877.906.944 GB (millions of Terrabyte!!) onto your harddrive
would require several hundreds of Terrabytes before you reach the end of the
generator. Don't you think that this is enough?
Nick Josipovic
CRM Administration
BIT-Institute
Prof. Dr. Franz Steffens
Schloss
68163 Mannheim
Germany
Phone: ++49 621 181-1621
Fax: ++49 621 181-1618
mailto:nick.josipovic@...
> -----Original Message-----
> From: zifnabbe@...
> [mailto:zifnabbe@...]
> Sent: Thursday, November 15, 2001 7:03 PM
> To: IBObjects@yahoogroups.com
> Subject: [IBO] info on database design
>