2009/3/13 <mich...@j3ksolutions.com>: >> I have a database logging weather data. When a station does not report a >> temperature, it is set to NULL. It would be a very bad idea to set it to 0 >> as this would ruin the whole statistics. >> NULL is a perfectly valid information in many cases. > I'd use -99999.9999, I'd never allow a "i don't know what it is" value > like Null in my database. what about a sensor that reports -99999.9999 when it is broken or the temperature is "out of range" for it? How could you express this information in this case? Just changing your fake-NULL value to -88888.8888 would be something *horrible*. I perfectly agree with Thomas, and I would expand his idea: - sensor working: integer value between -250~+32767 - sensor now working: integer value less than -250 - sensor unavailable: NULL I think that the advantages of this kind of architecture are easy to understand. More generally, NULL means (in this case): I cannot write a *value* because I have no informations, instead, -99999.9999 is a *value*! In a previous e-mail on this thread you wrote: "NULL is garbage" or something like this, but think: -99999.9999 is garbage. NULL is something we all agree, in general, it means "I don't know". Going back to the fax-number example, you wrote (if I correctly remember) that you would use some blanks, instead ... well, I would use a single zero character, and another could use some other value.... it would be a disaster! How could you avoid this?
Greetings, Mattia. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
