Abstract
Our notion of queries is as abstract as our notion of databases. Therefore, we may talk about different levels of query abstraction, just as we talked about different levels of data abstraction. In the previous chapters we usually thought of queries as functions from (possibly) infinite relational databases to (possibly) infinite relational databases as shown in Figure 23.1. This is the logical level of query abstraction. This level was enough to write good queries. However, in this chapter we consider queries at the constraint level. At the constraint level, queries can be thought of as functions from finite constraint databases to finite constraint databases, as shown in Figure 23.2.
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© 2010 Springer-Verlag London
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Revesz, P. (2010). Evaluation of Queries. In: Introduction to Databases. Texts in Computer Science. Springer, London. https://doi.org/10.1007/978-1-84996-095-3_23
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DOI: https://doi.org/10.1007/978-1-84996-095-3_23
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