Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Query by Example (QBE) is a database query language for relational databases. It was devised by Moshe M. Zloof at IBM Research during the mid 1970s, in parallel to the development of SQL. It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions. Many graphical front-ends for databases use the ideas from QBE today. Based on the notion of Domain relational calculus, QBE can be used as a search tool as well. A QBE parser parses the search query and looks for the keywords while eliminating words like a, an or the. A more formal query string, in languages such as SQL, is then generated, which is finally executed. However, when compared with a formal query, the results in the QBE system will be more variable.

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