|
|
Posted by Erland Sommarskog on 12/20/05 13:45
serge (sergea@nospam.ehmail.com) writes:
> I was working on figuring out where a certain application was
> storing the multiple selection choices I was doing through the app.
> I finally figured out that they were being store in an IMAGE
> data type colum with the variable length of 26 bytes.
>
> This is the first time I ran into such way of storing multiple
> selections in a single Image data type.
>
> Is this a better alternative than to store into a One-to-Many
> tables? If so then I'll have to consider using the Image data
> type approach next time I have to do something like storing
> 1 to thousands of selections.
One wonders if the length is a mere 26 bytes, why they used image. A
varbinary or binary would do.
I can't say that I like this design. The only time I find it defendable,
is if the database don't have any information of the individual bits,
but they are handled exclusively by the application and the database is
just a place where the application saves its persistent data. I would
expect that to be a technical application for process monitoring or
some such. One real-world example is the system tables in SQL Server.
Several of these have status columns that are bit masks. (They are
integer though.)
For storing selection choices, I would much rather prefer to use a table
with a row for each choice. A bit mask certainly violates the principle
of no repeating groups.
--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se
Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx
Navigation:
[Reply to this message]
|