I have 10 of these files in my collection. So my question is how can I query all these Xml files at ones and get specific results like "Books with price value greater than 100".
Use a simple XPath expression [1], such as
collection("name-of-collection"//Books[Price > 100]
You mentioned our REST service, which can also be used for that [2]:
http://localhost:8984/rest/name-of-collection?query=//Books...
Once I get these results I want to store the result in a RDBMS so that at later point I can query that RDBMS to generate certain reports.
Check out the SQL Module of our documentation [3] and give it a try.
Regards, Christian
[1] http://www.w3schools.com/xpath/ [2] http://docs.basex.org/wiki/REST [3] http://docs.basex.org/wiki/SQL