Page 214 - DCAP603_DATAWARE_HOUSING_AND_DATAMINING

Data Warehousing and Data Mining

notes covers the basic principles of query evaluation, the cost of query evaluation, the evaluation of
join queries, etc. in detail. It also provides information about query evaluation plans and the role
of storage in query evaluation and optimisation.

11.1 Query processing: an overview

Figure 11.1 show the processing of a query.

figure 11.1: Query processing

In the first step Scanning, Parsing, and Validating is done to translate the query into its internal
form. This is then further translated into relational algebra (an intermediate query form). Parser
checks syntax and verifies relations. The query then is optimised with a query plan, which then
is compiled into a code that can be executed by the database runtime processor.

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