Search data structure: Difference between revisions

Revision as of 21:36, 27 October 2022

Revision as of 14:06, 13 November 2022

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The simplest kind of query is to locate a record that has a specific field (the ''key'') equal to a specified value ''v''. Other common kinds of query are "find the item with smallest (or largest) key value", "find the item with largest key value not exceeding ''v''", "find all items with key values between specified bounds ''v''_min and ''v''_max".

In certain databases the key values may be points in some [[dimension (mathematics)|multi-dimensional space]]. For example, the key may be a geographic position ([[latitude]] and [[longitude]]) on the [[Earth]]. In that case, common kinds of queries are ''"find the record with a key closest to a given point ''v''", or "find all items whose key lies at a given distance from ''v''", or "find all items within a specified region ''R'' of the space".

A common special case of the latter are simultaneous range queries on two or more simple keys, such as "find all employee records with salary between 50,000 and 100,000 and hired between 1995 and 2007".