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In computer science, a lookup table (LUT) is an array that replaces runtime computation with a simpler array indexing operation, in a process termed as direct addressing.The savings in processing time can be significant, because retrieving a value from memory is often faster than carrying out an "expensive" computation or input/output operation. [1]
Crosswalk tables are often employed within or in parallel to enterprise systems, especially when multiple systems are interfaced or when the system includes legacy system data. In the context of Interfaces, they function as an internal extract, transform, load (ETL) mechanism. For example, this is a metadata crosswalk from MARC standards to ...
The MultiDimensional eXpressions (MDX) language provides a specialized syntax for querying and manipulating the multidimensional data stored in OLAP cubes. [1] While it is possible to translate some of these into traditional SQL, it would frequently require the synthesis of clumsy SQL expressions even for very simple MDX expressions.
SQLite: A VIEW named "dual" that works the same as the Oracle "dual" table can be created as follows: CREATE VIEW dual AS SELECT 'x' AS dummy; SAP HANA has a table called DUMMY that works the same as the Oracle "dual" table. Teradata database does not require a dummy table. Queries like 'select 1 + 1' can be run without a "from" clause/table name.
When there are multiple operations addressing the same key within one batch, the batch is condensed before being sent out. For example, multiple lookups of the same key can be reduced to one or multiple increments can be reduced to a single add operation. This reduction can be implemented with the help of a temporary local hash table.
In SQL Server 2012, an in-memory technology called xVelocity column-store indexes targeted for data-warehouse workloads. Mimer SQL: Mimer Information Technology SQL, ODBC, JDBC, ADO.NET, Embedded SQL, C, C++, Python Proprietary Mimer SQL is a general purpose relational database server that can be configured to run fully in-memory.
In computer science, and specifically in compiler and assembler design, a literal pool is a lookup table used to hold literals during assembly and execution.. Multiple (local) literal pools are typically used only for computer architectures that lack branch instructions for long jumps, or have a set of instructions optimized for shorter jumps.
The reason is quite simple: any lookup table that takes an extremely long time to compute also takes up an extremely large amount of space. Space is the fundamental limitation. Say you have a 10 terabyte drive filled with a lookup table and each element takes a microsecond to compute. Then the total time is only 16 weeks, which isn't that bad.