This should get you what you need:
Code:
select t1.*
from customer t1, contact t2
where t1.customerID = t2.customerID
and userInput_ID = t2.contactID
and userInput_Password = t2.contactPassword
Please (anyone), feel free to comment, as my SQL isn't what it could be. ;-) BTW, t1.* probably won't work, its just pseudo code, for any columns in customer you want.