Posted by Erland Sommarskog on 05/28/07 11:10

D. (d@d.com) writes:
> I'm planning the structure of a SqlServer 2005 database for a new
> application.
> The requirement is that primary keys must be "natural"; i.e. in the table
> Customers the primary key will be a max. 10 characters string (but the
> string may be filled i.e. with only 5 charachters).
>
> Should I define these primary keys as char[5] or varchar[5]?
> I'm interested in your opinion in particular about performace issue,
> because there will be tables with millions of records...

char(10) would make sense if key values are almost always 10 characters
long, but if the distribution varies with, say, 5 as the average varchar
would be better.

What sort of strings do you expect? If the values will be digits and upper-
case characters, you way want to consider a binary collation for the column,
at least if your default collation is a Windows collation.


--
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

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