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Reverse Index
Database management systems provide multiple types of indexes to improve performance and data integrity across diverse applications. Index types include b-trees, bitmaps, and r-trees. In database management systems, a reverse key index strategy reverses the key value before entering it in the index. E.g., the value 24538 becomes 83542 in the index. Reversing the key value is particularly useful for indexing data such as sequence numbers, where each new key value is greater than the prior value, i.e., values monotonically increase. Reverse key indexes have become particularly important in high volume transaction processing systems because they reduce contention for index blocks. Creating data Reversed key indexes use b-tree structures, but preprocess key values before inserting them. Simplifying, b-trees place similar values on a single index block, e.g., storing 24538 on the same block as 24539. This makes them efficient both for looking up a specific value and for finding val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Management Systems
In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an application associated with the database. Before digital storage and retrieval of data have become widespread, index cards were used for data storage in a wide range of applications and environments: in the home to record and store recipes, shopping lists, contact information and other organizational data; in business to record presentation notes, project research and notes, and contact information; in schools as flash card ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Index (database)
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. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random lookups and efficient access of ordered records. An index is a copy of selected columns of data, from a table, that is designed to enable very efficient search. An index normally includes a "key" or direct link to the original row of data from which it was copied, to allow the complete row to be retrieved efficiently. Some databases extend the power of indexing by letting developers create indexes on column values that have been transformed by functions or expressions. For example, an index could be created on upper(last_name), which would o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
