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In relational databases a virtual column is a table column whose value(s) is automatically computed using other columns values, or another deterministic expression. Virtual columns are defined of SQL:2003 as Generated Column, [1] and are only implemented by some DBMSs, like MariaDB, SQL Server, Oracle, PostgreSQL, SQLite and Firebird (database server) (COMPUTED BY syntax).
The algorithm development in this direction has an advantage of low complexity. Because this is a customized approach, existing database systems cannot flatten arbitrary correlated subqueries by following certain general rules. In addition, this approach requires high engineering efforts to implement flattening algorithms into a database engine.
SpatiaLite is a spatial extension to SQLite, providing vector geodatabase functionality. It is similar to PostGIS, Oracle Spatial, and SQL Server with spatial extensions, although SQLite/SpatiaLite aren't based on client-server architecture: they adopt a simpler personal architecture. i.e. the whole SQL engine is directly embedded within the application itself: a complete database simply is an ...
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.
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] 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 ...
Note (2): Can be implemented for most data types using expression-based indexes. Note (3): Can be emulated by indexing a computed column [122] (doesn't easily update) or by using an "Indexed View" [123] (proper name not just any view works [124]). Note (4): Used for InMemory ColumnStore index, temporary hash index for hash join, Non/Cluster ...
phpLiteAdmin is an open-source tool written in PHP intended to handle the administration of SQLite over the World Wide Web. Its feature set, interface, and overall user experience is comparable to that of phpMyAdmin for MySQL.
The idea is that the first clusters will add much information (explain a lot of variation), since the data actually consist of that many groups (so these clusters are necessary), but once the number of clusters exceeds the actual number of groups in the data, the added information will drop sharply, because it is just subdividing the actual groups.