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  2. Query evaluation - Wikipedia

    en.wikipedia.org/wiki/Query_evaluation

    In database theory, the query evaluation problem is the problem [verification needed] of determining the answers to a query on a database. Research in database theory aims at determining the computational complexity of answering different kinds of queries over databases, in particular over relational databases .

  3. 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 ...

  4. Query expansion - Wikipedia

    en.wikipedia.org/wiki/Query_expansion

    Machine learning based query term weight and synonym analyzer for query expansion. LucQE - open-source, Java. Provides a framework along with several implementations that allow to perform query expansion with the use of Apache Lucene. Xapian is an open-source search library which includes support for query expansion; ReQue open-source, Python ...

  5. View (SQL) - Wikipedia

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

    This pre-established query command is kept in the data dictionary. Unlike ordinary base tables in a relational database, a view does not form part of the physical schema: as a result set, it is a virtual table [1] computed or collated dynamically from data

  6. Online analytical processing - Wikipedia

    en.wikipedia.org/wiki/Online_analytical_processing

    In essence, each action of slicing and dicing is equivalent to adding a "WHERE" clause in the SQL statement. ROLAP tools do not use pre-calculated data cubes but instead pose the query to the standard relational database and its tables in order to bring back the data required to answer the question.

  7. Star schema - Wikipedia

    en.wikipedia.org/wiki/Star_schema

    Star schema used by example query. Consider a database of sales, perhaps from a store chain, classified by date, store and product. The image of the schema to the right is a star schema version of the sample schema provided in the snowflake schema article.

  8. Aggregate (data warehouse) - Wikipedia

    en.wikipedia.org/wiki/Aggregate_(data_warehouse)

    An aggregate is a type of summary used in dimensional models of data warehouses to shorten the time it takes to provide answers to typical queries on large sets of data. The reason why aggregates can make such a dramatic increase in the performance of a data warehouse is the reduction of the number of rows to be accessed when responding to a ...

  9. Query plan - Wikipedia

    en.wikipedia.org/wiki/Query_plan

    A query plan (or query execution plan) is a sequence of steps used to access data in a SQL relational database management system. This is a specific case of the relational model concept of access plans.