"what query should we run to get record for one selection of dropdownlist box or
for selection of more than one..."
It would vary depending on your DB design. If the fields are all in the same table, it's relatively simple:
SELECT * FROM MyTable WHERE <condition1> OR <Condition2>
Or
SELECT * FROM MyTable WHERE <condition1> AND <Condition2>
But if they are in different tables, then it gets more complex: potentially a lot more complex.
We can't tell - we don't know what your columns are, your drop downs contain, anything realy. Remember that we can't see your screen, access your HDD, or read your mind! :laugh:
So start by looking at what info you are trying to fetch, and run up queries for various collections of them. It should become fairly obvious with a bit of thinking what you need to do.