search

i want to search acoording to firstname ,lastname, city ,state, country and email id of all the registered users.....
i hv used one textbox for the search.....
but i am now trouble that how i identify that user hv entered only firstname or firstname and lastname or firstname ,lastname and country or firstname ,lastname and city or firstname ,lastname and state or firstname ,lastname, city ,state and country...
or he had entered the emailid ....

here i hv only one textbox which takes the value anyone who want to search...........
how can differentiate them from each other and can search the desired result..........