Ad-Hoc Query

"ad hoc" reporting systems allow the users themselves to create specific, customized queries.
Typically this would be via a user-friendly GUI-based system without the need for the in-depth knowledge of SQL, or database schema that a programmer would have.
Because such reporting has the potential to severely degrade the performance of a live system, it is usually provided over a data warehouse.
Ad hoc querying/reporting is a business intelligence subtopic, along with OLAP, data warehousing, data mining and other tools.
http://en.wikipedia.org/wiki/Ad_hoc

An Ad-Hoc Query is a query that cannot be determined prior to the moment the query is issued.
It is created in order to get information when need arises and it consists of dynamically constructed SQL which is usually constructed by desktop-resident query tools.
http://www.learn.geekinterview.com/data-warehouse/dw-basics/what-is-an-ad-hoc-query.html