Hi Jim, If I understand your requirements correctly, I think you need just 3 tables. Your item/product table will contain a unique item number plus any other fields (name, description, etc.) pertaining to the item/product. Your category table will contain a unique category number, a parent category number and the category name. The parent category field contains the category number of the parent category. If it's a top level category, the parent category field contains 0 or null. The third table, call it the categorization table, contains an item number field and a category field. These fields are not unique. You can have an item in more than one category. If you want to see a php script implementing categories, feel free to download my FAQ script from my website at: http://www.AnoeticConcepts.com/ Regarding database books, I thought the SQL in 21 days which I got from your website was pretty good. Good luck. Jeff ----- Original Message ----- From: <james.homme@xxxxxxxxxxxx> Sent: Thursday, September 13, 2007 4:27 AM Hi, Time to get an SQL book. Has anyone here read Database Design For Mere Mortals? How did you like it? What other database design books are good? One of my concerns is that they usually talk all about the stupid diagrams you have to make and read and not about the concepts. I want to understand the kinds of relationships you can make and how to query and get what I want out of the database. Thanks for any and all help. Jim __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind