what are you using to create the database? if you store the chair number as the first key, then when someone asks for the location of the chair you can perform a modified binary search to get the chair entry, consequently the chair's location.
To see what is available you can search the location key for "On Site" and list the results sorted by chair number.

The easiest way to make the location key is to enumerate the locations ie:

0 = On Site
1 = Off Site
2 = Out Of Service
3 = In Storage

then search the corrseponding numerical equivalent value. Hope this helps