1. The retrieval of information from a database according to a set of retrieval criteria, the database itself remaining unchanged.
2. In the context of a specific query language, the technique of translating the retrieval criteria specified using the language (see def. 1) into more primitive database-access software, including a selection among different methods to choose the most efficient in the particular circumstances.
"query processing." A Dictionary of Computing. . Encyclopedia.com. (August 19, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/query-processing
"query processing." A Dictionary of Computing. . Retrieved August 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/query-processing