QBE (Query by example)
QBE (Query by example) is a method of creation of database requests, using samples in the form of a text line, document title or the document list. The QBE system will transform the user input to a formal database request that allows the user to make advanced queries without need to learn more difficult languages of requests such as SQL. This method of selection of data is for the first time offered by IBM company in 1970.
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Advantage of search of QBE is that for formation of a request it is not required to learn language of requests. When you initiate search, the window in which all data fields which are found in each data writing are specified is displayed; enter information which limits search only to the specified criteria: that field which will not be filled can correspond to anything.
In fact the QBE language is mixed as at it there are also elements of calculation of trains.
There are several commercial implementations of the QBE language, or "QBE-like" language. QBE intended for the users interested in selection of information of databases. This language gained so wide recognition at users that now to some extent it is implemented practically in all popular DBMS, including also Microsoft Access. Means of the QBE language can be used for input of requests to information saved in one or several tables and also for determination of set of fields which should be present at the resulting table. Selection of records can be made on a specific or general criterion and provide accomplishment of necessary calculations on the basis of information saved in tables. Besides, means of the QBE language can be used for accomplishment of different transactions over tables, for example, for an insert and removal of records, modification of field values or creation of new fields and tables.
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