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A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time said table is accessed.
Database tables and indexes may be stored on disk in one of a number of forms, including ordered/unordered flat files, ISAM, heap files, hash buckets, or B+ trees. Each form has its own particular advantages and disadvantages. The most commonly used forms are B-trees and ISAM.
Download QR code; Print/export ... This category includes indexing techniques for database management systems. ... Pages in category "Database index techniques" ...
A database system where an application developer directly uses an application programming interface to search indexes in order to locate records in data files. In contrast, a relational database uses a query optimizer which automatically selects indexes. [2] An indexing algorithm that allows both sequential and keyed access to data. [3]
A bitmap index is a special kind of database index that uses bitmaps. Bitmap indexes have traditionally been considered to work well for low- cardinality columns , which have a modest number of distinct values, either absolutely, or relative to the number of records that contain the data.
Download QR code; Print/export Download as PDF; Printable version ... move to sidebar hide. A database composite index or multi-column index is an index that is based ...
Within computing and computer science, an expression index, also known as a function based index, is a database index that is built on a generic expression, rather than one or more columns. This allows indexes to be defined for common query conditions that depend on data in a table, but are not actually stored in that table.
Sources: [2] [3] Consider a database containing data from a census. A single record represents a single household, and all records are grouped into buckets. All records in a bucket can be indexed by either their city (which is the same for all records in the bucket), and the streets in that city whose names begin with the same letter.