By means of a query, you retrieve data from a database. In this chapter we’ll demonstrate how you can specify a query in a formal way. To do so, we won’t require the formal introduction of any new concepts; we’ve already presented all ingredients for specifying queries.
The section “Formally Specifying Queries” introduces you to the formal concept of a query over a database universe. You’ll find out that you can specify a query as a set-theory expression based on a given database state. In this section, we’ll also give a few simple examples to familiarize you with this formal concept of a query.
The section “Example Queries Over DB_UEX” provides ...
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