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QBE Query-By-Example

Introduction. Query By Example (QBE)QBE and its variants are widely used in database system on PCs.QBE is the name of both a data-manipulation language and an early database that included this language.QBE database system was developed at IBM's T.J.Watson Research Center in the early 1970's.. Ov

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QBE Query-By-Example

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    1. QBE Query-By-Example Presented by Angela Tong CS157A Dr. Sin Min Lee

    2. Introduction Query By Example (QBE) QBE and its variants are widely used in database system on PCs. QBE is the name of both a data-manipulation language and an early database that included this language. QBE database system was developed at IBM’s T.J.Watson Research Center in the early 1970’s.

    3. Overview Basic Structure Queries on One Relation Queries on Several Relations The Condition Box The Result Relation Ordering the Display of Tuples Aggregate Operations Modifying the Database Deletion Insertion Updates QBE in Microsoft Access

    4. Basic Structure QBE has two-dimensional syntax: Queries look like tables. QBE queries are expressed “by example”. Close correspondence with domain relational calculus. Non-procedural. Queries are expressed using skeleton tables. User selects the skeletons needed. User fills in skeletons with example rows. An example row consists of constants and example elements which are really domain variable. Domain variables are preceded by an underscore character. Constants appear without any qualification.

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