Re: set type and normalize

[Brent Baisley]

As mentioned in the manual you specified, there are limits to how many 
items you can have in a set, among other issues. My biggest issue 
against using sets is that you need alter the table structure whenever 
you want to change the set.  Usually I would want the user to be able 
to add, modify or delete list items. You do NOT want a user being able 
to alter the table structure.
The three table layout gives you basically unlimited scalability, 
easier and quicker modification, dynamic sorting, more flexible 
searching and no character restrictions.

On Apr 7, 2005, at 5:20 PM, Marilyn Davis wrote:
Hi MySQL people.
I'm trying to understand the pros and cons of the "set" column type.
Here is an excerpt from the article:
http://dev.mysql.com/tech-resources/articles/mysql-set-datatype.html
      Why You Shouldn't Use SET
"Third, using a set means your data is not normalized. In our above
example, we are tracking a person's interests for a hypothetical
dating site. In a normalized schema, there should be three tables: one
for the person, one for all possible interests, and one that links a
person to their particular interests."
The "above example" is:
  CREATE TABLE set_test(
    rowid INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    myset SET('Travel','Sports','Dancing','Fine Dining')
  );
I guess I'm not understanding the point here.  What practical
advantage is there to creating three tables instead of using a set
column type?
Thank you for any help.
Marilyn Davis

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Brent Baisley
Systems Architect
Landover Associates, Inc.
Search & Advisory Services for Advanced Technology Environments
p: 212.759.6400/800.759.0577
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