At 4:33 PM -0400 8/29/09, [email protected] wrote:
Daniel Convissor wrote:
This is useful, in part, for statistical purposes, since the null record
won't be added into averages, etc. For example, you had three surveys
filled out. Two people actually filled in their ages (10 and 20), if you
do an average when using nulls, you'll get an average age of 15. But if
you use 0's instead of nulls, the average age will incorrectly be 10.
Dan, this is very helpful--thank you! The light bulb is starting to come
on in my head now...
If anyone else has practical examples, please don't hold back.
Bev
Null is an odd critter. It's not an empty string, it's not '', it's
not 0, it's NULL.
Try reading this:
http://dev.mysql.com/doc/refman/5.0/en/problems-with-null.html
Cheers,
tedd
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