"1. A request for the retrieval of data with a select statement. 2. Any SQL statement that manipulates data." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)
"A specific request for data retrieval, modification, or deletion." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)
"A SELECT statement." (Peter Gulutzan & Trudy Pelzer, "SQL Performance Tuning", 2002)
"A request for information based on the value of certain fields against a database or a data warehouse." (Margaret Y Chu, "Blissful Data ", 2004)
"A SQL SELECT statement that extracts data from a database." (Rod Stephens, "Beginning Database Design Solutions", 2008)
"The mechanism to get data out of a database. A query is comprised of constraints used to filter data out of the results, and defines the data elements to be included in the result set and possibly some mathematical computations, grouping, or sorting of the data." (Laura Reeves, "A Manager's Guide to Data Warehousing", 2009)
"A computing function that requests data from the database, stating the parameters and constraints for the request." (Paulraj Ponniah, "Data Warehousing Fundamentals for IT Professionals", 2010)
"(1) A SQL SELECT statement written and issued against a database. (2) To request data from a database." (Craig S Mullins, "Database Administration", 2012)
"An operation that retrieves data from tables or views. For example, SELECT * FROM employees is a query." (Oracle, "Database SQL Tuning Guide Glossary", 2013)
"A procedure executed by a computer program in search of qualified data" (Daniel Linstedt & W H Inmon, "Data Architecture: A Primer for the Data Scientist", 2014)
"A request for information from a database that is based on specific conditions: for example, a request for a list of all customers in a customer table whose balances are greater than USD1000. A component of certain SQL or XQuery statements that specifies a result set." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)
"A type of question accepted by a database about the data it holds. A complex query may ask the database to select records according to some criteria, aggregate certain quantities across those records, etc. Many databases accept queries in the specialised language SQL or dialects of it." (Open Data Handbook)