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For example, Microsoft SQL Server implements cursors by creating a temporary table and populating it with the query's result set. If a cursor is not properly closed ( deallocated ), the resources will not be freed until the SQL session (connection) itself is closed.
Query by Example (QBE) is a database query language for relational databases. It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL . [ 1 ] It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions.
SQLite (/ ˌ ɛ s ˌ k juː ˌ ɛ l ˈ aɪ t /, [4] [5] / ˈ s iː k w ə ˌ l aɪ t / [6]) is a free and open-source relational database engine written in the C programming language.It is not a standalone app; rather, it is a library that software developers embed in their apps.
Queries can be nested so that the results of one query can be used in another query via a relational operator or aggregation function. A nested query is also known as a subquery. While joins and other table operations provide computationally superior (i.e. faster) alternatives in many cases, the use of subqueries introduces a hierarchy in ...
Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.
Queries can be nested so that the results of one query can be used in another query via a relational operator or aggregation function. A nested query is also known as a subquery . While joins and other table operations provide computationally superior (i.e. faster) alternatives in many cases (all depending on implementation), the use of ...
For the special case of conjunctive queries in which all relations used are binary, this notion corresponds to the treewidth of the dependency graph of the variables in the query (i.e., the graph having the variables of the query as nodes and an undirected edge {,} between two variables if and only if there is an atomic formula (,) or (,) in ...
The following tables compare general and technical information for a number of available database administration tools. Please see individual product articles for further information. This article is neither all-inclusive nor necessarily up to date. Systems listed on a light purple background are no longer in active development.