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Query-by-Example: A data base language

 Award plaque by M. M. Zloof

Discussed is a high-level data base management language that provides the user with a convenient and unified interface to query, update, define, and control a data base. When the user performs an operation against the data base, he fills in an example of a solution to that operation in skeleton tables that can be associated with actual tables in the data base. The system is currently being used experimentally for various applications.

Originally published:

IBM Systems Journal, Volume 16, Issue 4, pp. 324-343 (1977).

Significance:

Query-by-Example (QBE) is a high-level database management language that provides a convenient and unified approach for queries, updates, and controls of a relational database. The philosophy of Query-by-Example permits new users to employ database applications with little effort, and QBE minimizes the number of concepts that must be learned in order to understand and use the language. The language syntax is simple but covers a wide variety of complex transactions.

This very highly cited paper describes QBE for relational databases and provides numerous examples of its use. Devised by Moshé M. Zloof at IBM Research during the mid-1970s, QBE was one of the first graphical query languages that used “visual” tables in which the user entered commands and conditions. Today, many databases use graphical front ends that have their genesis in QBE and related database languages.

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