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  2. Query optimization - Wikipedia

    en.wikipedia.org/wiki/Query_optimization

    The query optimizer attempts to determine the most efficient way to execute a given query by considering the possible query plans. [1] Generally, the query optimizer cannot be accessed directly by users: once queries are submitted to the database server, and parsed by the parser, they are then passed to the query optimizer where optimization ...

  3. Query plan - Wikipedia

    en.wikipedia.org/wiki/Query_plan

    Some query tools can generate embedded hints in the query, for use by the optimizer. Some databases - like Oracle - provide a plan table for query tuning. This plan table will return the cost and time for executing a query. Oracle offers two optimization approaches: CBO or Cost Based Optimization; RBO or Rule Based Optimization

  4. Query rewriting - Wikipedia

    en.wikipedia.org/wiki/Query_Rewriting

    Query rewriting is a typically automatic transformation that takes a set of database tables, views, and/or queries, usually indices, often gathered data and query statistics, and other metadata, and yields a set of different queries, which produce the same results but execute with better performance (for example, faster, or with lower memory use). [1]

  5. Select (SQL) - Wikipedia

    en.wikipedia.org/wiki/Select_(SQL)

    This functionality is called the "query optimizer" as it is responsible for finding the best possible execution plan for the query, within applicable constraints. The SELECT statement has many optional clauses: SELECT list is the list of columns or SQL expressions to be returned by the query.

  6. Hint (SQL) - Wikipedia

    en.wikipedia.org/wiki/Hint_(SQL)

    In various SQL implementations, a hint is an addition to the SQL standard that instructs the database engine on how to execute the query. For example, a hint may tell the engine to use or not to use an index (even if the query optimizer would decide otherwise).

  7. Database tuning - Wikipedia

    en.wikipedia.org/wiki/Database_tuning

    Database tuning describes a group of activities used to optimize and homogenize the performance of a database.It usually overlaps with query tuning, but refers to design of the database files, selection of the database management system (DBMS) application, and configuration of the database's environment (operating system, CPU, etc.).

  8. Patricia Selinger - Wikipedia

    en.wikipedia.org/wiki/Patricia_Selinger

    She played a fundamental role in the development of System R, a pioneering relational database implementation, and wrote the canonical paper on relational query optimization. [2] She is a pioneer in relational database management and inventor of the technique of cost-based query optimization.

  9. Join (SQL) - Wikipedia

    en.wikipedia.org/wiki/Join_(SQL)

    A query optimizer determines how to execute a query containing joins. A query optimizer has two basic freedoms: A query optimizer has two basic freedoms: Join order : Because it joins functions commutatively and associatively, the order in which the system joins tables does not change the final result set of the query.