You use a series of binary switches to determine what class can use that item:
Code:
D W M S P R H P W
R A A H R O U A A
U L G A I G N L R
0 0 0 0 0 0 1 0 0 = 4 = HUNTER
0 0 1 0 0 0 0 0 0 = 64 = MAGE
0 0 0 0 0 0 0 1 1 = 3 = WARRIOR + PALADIN
NOTE: You can use calculator to convert from binary to decimal.
This is VERY easy and simple. I'l explain a bit better:
9 = Druid, 8 = Warlock, 7 = Mage, 6 = Shaman, 5 = Priest, 4 = Rogue, 3 = Hunter, 2 = Paladin, 1 = Warrior
The binary code is arranged like this:
9 8 7 6 5 4 3 2 1
All you do is, if you want a certain class to be able to wear an item, place a "1" in it's slot (in the above arrangement), then replace all others with 0. Then, open calculator, click on "View", then click "Scientific".
You'll then see 4 radio boxes (Hex, Dec, Oct, Bin). Select "Bin", type in the binary code, then click on "Dec". Then, you can use the resulting number in the "RequiredClass" column in your database.