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Query by Example (QBE) is a database query language for relational databases. It was devised by Moshé 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. QBE is based on the notion of Domain relational calculus.
Example A simple example using the Suppliers and Parts database is given here, just to give you a feel for how QBE works. This "query" selects all supplier numbers (S Other commands like the "P." (print) command are: "U." (update), "I." (insert) and "D." (delete). The result of this query depends on what the values are for your the Suppliers and Parts database. See also QBE Query by Example (QBE) is a powerful search tool that allows anyone to search a system for document(s) by entering an element such as a text string or document name, quickly searching through documents to match your entered criteria. It’s commonly believed that QBE is far easier to learn than other, more formal query languages, (i.e. SQL) while still providing people with the opportunity to perform powerful searches. Searching for documents based on matching text is easy with QBE; the user simply enters (or copy and paste) the target text into the search form field. When the user clicks search (or hits enter) the input is passed to the QBE parser for processing. The query is created and then the search begins, using key words from the input the user provided. It auto-eliminates mundane words such as and, is, or, the, etc… to make the search more efficient and not to barrage the user with results. However, when compared with a formal query, the results in the QBE system will be more variable. The user can also search for similar documents based on the text of a full document that he or she may have. This is accomplished by the user’s submission of documents (or numerous documents) to the QBE results template. The analysis of these document(s) the user has inputted via the QBE parser will generate the required query and submits it to the search engine, that will obviously then search for relevant and similar material for the specified list. Sources | ||||||||
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