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In a database, a query that is not indexed results in a full table scan, where the database processes each record of the table to find all records meeting the given requirements. Even if the query selects just a few rows from the table, all rows in the entire table will be examined.
To process this statement without an index the database software must look at the last_name column on every row in the table (this is known as a full table scan). With an index the database simply follows the index data structure (typically a B-tree) until the Smith entry has been found; this is much less computationally expensive than a full ...
Since surrogate keys replace a table's identifying attributes—the natural key—and since the identifying attributes are likely to be those queried, then the query optimizer is forced to perform a full table scan when fulfilling likely queries. The remedy to the full table scan is to apply indexes on the identifying attributes, or sets of them.
Full table scan; H. ... Regular path query; Relational database; ... Single Table Inheritance; Supra-entity; Symposium on Principles of Database Systems; T.
Denormalization combines related data into a single table, and composite keys or secondary indexes allow efficient grouping and querying of related items. Application-level joins merge results programmatically from multiple queries, while single-table design pre-joins data during schema planning.
Restaurant portions can be enormous today, so it's no surprise that those who dine out may feel stuffed to the gills with half their meal still on the plate.. In these scenarios, servers often ...
The set of query plans examined is formed by examining the possible access paths (e.g., primary index access, secondary index access, full file scan) and various relational table join techniques (e.g., merge join, hash join, product join). The search space can become quite large depending on the complexity of the SQL query. There are two types ...
The NBA Christmas Day quintuple-header offered some star performances and interesting results, but the calendar rolls on with a full weekend slate. On Friday, fans will get a rematch of the ...