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In digital logic, a lookup table can be implemented with a multiplexer whose select lines are driven by the address signal and whose inputs are the values of the elements contained in the array. These values can either be hard-wired, as in an ASIC whose purpose is specific to a function, or provided by D latches which allow for configurable values.
Some applications simply want the newest key-value pair with a given key. Some applications must combine the values in some way to get the proper aggregate value to return. For example, in Apache Cassandra, each value represents a row in a database, and different versions of the row may have different sets of columns. [4]
A SQL query to a modern relational DBMS does more than just selections and joins. In particular, SQL queries often nest several layers of SPJ blocks (Select-Project-Join), by means of group by, exists, and not exists operators. In some cases such nested SQL queries can be flattened into a select-project-join query, but not always. Query plans ...
A database management system (DBMS) is a computer program (or more typically, a suite of them) designed to manage a database, a large set of structured data, and run operations on the data requested by numerous users. Typical examples of DBMS use include accounting, human resources and customer support systems.
Interactive access to the Oracle Rdb can be by SQL (Structured Query Language), RDO (Relational Database Operator), or both. High level languages usually access Oracle-Rdb by: embedding RDO statements in the source file then running it through a precompiler (example: "file.RCO" is pre-compiled into "file.COB")
Database name Language implemented in Notes Apache Doris Java & C++ Open source (since 2017), database for high-concurrency point queries and high-throughput analysis. Apache Druid: Java Started in 2011 for low-latency massive ingestion and queries. Support and extensions available from Imply Data. Apache Kudu: C++
The basic data structure of the relational model is the table, where information about a particular entity (say, an employee) is represented in rows (also called tuples) and columns. Thus, the "relation" in "relational database" refers to the various tables in the database; a relation is a set of tuples. The columns enumerate the various ...
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 ...