Re: a problem about database modeling

> i have a entity 'device' and every 'device' has there own 'type' and every 'type' has there specific attributes. first i let the table 'device' keep all common attributs of device ,but i find i can't keep the 'device's type attributes at least i found if i do that.it got be urgly and strangly. so what can i do about this thanks for any help.

Modelling such varied data (especially in a non-redundant / flexible manner) can require quite a few tables and joins. You may need to store each device's attributes/values in additional tables to avoid NULLs.

Your example sounds similar to www.dbfordummies.com/example/ex123.asp If you would like to post actual data, I can model/query it with dbd and someone else here can show the equivalent with an RMDB. Received on Wed Jul 19 2006 - 09:53:55 CDT