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Set operations (SQL) Set operations in SQL is a type of operations which allow the results of multiple queries to be combined into a single result set. [1] Set operators in SQL include UNION, INTERSECT, and EXCEPT, which mathematically correspond to the concepts of union, intersection and set difference .
A non-primary key that can be used to identify only one row in a table. Alternate keys may be used like a primary key in a single-table select. Foreign. A key that has migrated to another entity. At the most basic definition, "a key is a unique identifier", [1] so unique key is a pleonasm.
History. SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd in the early 1970s. This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
SELECT is the most common operation in SQL, called "the query". SELECT retrieves data from one or more tables, or expressions. Standard SELECT statements have no persistent effects on the database. Some non-standard implementations of SELECT can have persistent effects, such as the SELECT INTO syntax provided in some databases.
Access, the successor to ENGLISH, is an English -like query language used in the Pick operating system . The original name ENGLISH is something of a misnomer, as PICK's flexible dictionary structure meant that file and attribute names could be given aliases in any natural language. For instance the command SORT could be given the alias TRIEZ ...
Since every search engine is unique and has different algorithms for generating ranked data, duplicates will therefore also be generated. To remove duplicates, a metasearch engine processes this data and applies its own algorithm. A revised list is produced as an output for the user.
Universally unique identifier. A Universally Unique Identifier ( UUID) is a 128-bit label used for information in computer systems. The term Globally Unique Identifier ( GUID) is also used, mostly in Microsoft systems. [1] [2] When generated according to the standard methods, UUIDs are, for practical purposes, unique.
A query string is a part of a uniform resource locator (URL) that assigns values to specified parameters. A query string commonly includes fields added to a base URL by a Web browser or other client application, for example as part of an HTML document, choosing the appearance of a page, or jumping to positions in multimedia content.