Chuck OK, here are some recommendations, although I'm sure other folks will have some ideas:
1) PHP and MySQL Web Development: Welling/Thomas ISBN0-672-32525-X
Has a reasonable section on database schema design, but not that extensive.
2) Database Systems: Catherine Ricardo
Excellent book - unfortunately the ISBN # shown on the copy I've had for 15 years doesn't bring up ant results, but searching for Catherine Ricardo on amazon shows some more recent issues:
http://www.amazon.com/exec/obidos/search-handle-form/ref=s_sf_b_as/103-0082326-5928601
Finally, and the folks at MySQL aren't going to like me for this:
3) Informix-SQL - Tony Lacy-Thompson
Again, I've had this book for about 14 years. OK, it deals with Informix SQL, but the chapter on database design principles is worth the price alone. I worked with Tony on a couple of projects and, not only was he a real database guru - but a thoroughly nice guy as well. Once again it looks like it's out of print, but there are 2nd-hand copies going on amazon from $9.99 - worth every penny (cent) !
I've actually got two in mint condition, as I used to give them to delegates on training courses, but they ain't going anywhere ;-)
Hope this helps.
Nick
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Nick Roper