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Understanding Query Processing and Set Operators in SQL

This document provides a comprehensive overview of query processing in SQL, detailing various set operators and their applications. It presents schematic diagrams illustrating the Cartesian product of relations and the join operations, alongside examples of set operators. Additionally, the anatomy of a query focusing on courses taught by computer science professors is analyzed. SQL aggregate functions and the usage of the GROUP BY clause are also discussed, demonstrating the evaluation process and how views modify queries. Finally, the document explains SQL’s truth tables for dealing with unknowns in queries.

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Understanding Query Processing and Set Operators in SQL

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  1. Figure 6.1Schematic view of query processing.

  2. Figure 6.2AExamples of set operators.

  3. Figure 6.2B (continued)Examples of set operators.

  4. Figure 6.2C (continued)Examples of set operators.

  5. Figure 6.3Two relations and their Cartesian product.

  6. Figure 6.3B (continued)Two relations and their Cartesian product.

  7. Figure 6.4Join of relations in Figure 6.3.

  8. Figure 6.5Division operator.

  9. Figure 6.6Anatomy of a Query: Courses taught by every computer science professor.

  10. Figure 6.7SQL aggregate functions.

  11. Figure 6.8Effect of the GROUP BY clause.

  12. Figure 6.9Query evaluation with aggregate functions.

  13. Figure 6.10Process of query modification by views..

  14. Figure 6.11SQL’s truth tables used to deal with the unknown.

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