[Rails] Re: Learning some best DB practices

Also consider the demands of a very very rapidly changing field, like
medical informatics.  In this area, many prefer the flexibility of a
key/value system because adding columns constantly would be a
nightmare.  Think off adding columns for every new lab test, imaging
type, procedure, etc.  This is where a system like this is extremely
helpful.

Another addition that can sometimes be helpful is to add an additional
column that holds a "datatype" that represents a traditional database
constraint.  This allows for easy programmatic testing against this
datatype before the data enters the database.  Obviously this requires
some programming work up-front, but this can be exceedingly useful
once it is built.  Again, flexibility is the key here.

Some links:

http://ycmi.med.yale.edu/nadkarni/eav_CR_contents.htm
http://www.cdc.gov/nedss/DataModels/index.html
http://www.research.ibm.com/journal/sj/461/eggebraaten.html

Andrew

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