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Re: What is the advantage to this kind of database structure?

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From	Erland Sommarskog <esquel@sommarskog.se>
Newsgroups	comp.databases.ms-sqlserver
Subject	Re: What is the advantage to this kind of database structure?
Date	Wed, 25 May 2011 23:32:55 +0200
Organization	Erland Sommarskog
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stapes (steve.staple@gmail.com) writes:
> I have had to do maintenance work on a number of databases that have
> been created using what seems to me a very complex structure.
> 
> For instance, instead of having one table of information on members of
> staff, there are 20. Separate tables exist for items which are
> compulsory - such as Medical information, Criminal Records, etc. I can
> understand this in the case of optional items, which may or may not
> exist, such as Interview results, or items which may exist in
> multiples, such as References.
> 
> Is there any advantage to this kind of structure?

It's difficult to tell without seeing the full picture. But as Gene 
points out, cardinality is a big deal. If there is one row for each
offense in the CriminalRecords table, you can't have that data in the
main table.

But from what you say "CriminalRecord" is a single column, presumably
a blob column. Maybe someone thought it would be better to have them
separated for some not such a good reason, for instance because
they use SELECT * all over the place.

-- 
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se

Links for SQL Server Books Online:
SQL 2008: http://msdn.microsoft.com/en-us/sqlserver/cc514207.aspx
SQL 2005: http://msdn.microsoft.com/en-us/sqlserver/bb895970.aspx

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What is the advantage to this kind of database structure? stapes <steve.staple@gmail.com> - 2011-05-24 15:11 -0700
  Re: What is the advantage to this kind of database structure? Gene Wirchenko <genew@ocis.net> - 2011-05-24 15:34 -0700
  Re: What is the advantage to this kind of database structure? Erland Sommarskog <esquel@sommarskog.se> - 2011-05-25 23:32 +0200

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