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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.
Climbers of Mount Everest can use video call and other 3G services at the top of the mountain at no cost. LTE services have been installed in many base camps. Fixed line operators. CG Digital; Nepal Telecom; Mobile operators. SmartCell; Hello Nepal; Ncell GSM; Nepal Telecom GSM & CDMA both; United Telecom CDMA; Netherlands Mobile operators ...
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.
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.
Primary key. In the relational model of databases, a primary key is a specific choice of a minimal set of attributes ( columns) that uniquely specify a tuple ( row) in a relation ( table ). [a] [1] Informally, a primary key is "which attributes identify a record," and in simple cases constitute a single attribute: a unique ID.
Database index. 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.
SQL syntax. The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075. This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.