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To create a treemap, one must define a tiling algorithm, that is, a way to divide a region into sub-regions of specified areas.Ideally, a treemap algorithm would create regions that satisfy the following criteria:
Treemap: Treemap: size; color; Is a method for displaying hierarchical data using nested figures, usually rectangles. For example, disk space by location / file type; Gantt chart: Gantt chart: color; time (flow) Type of bar chart that illustrates a project schedule; Modern Gantt charts also show the dependency relationships between activities ...
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 ...
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
The Oxford English Dictionary records use of both the terms "tree structure" and "tree-diagram" from 1965 in Noam Chomsky's Aspects of the Theory of Syntax. [2] In a tree structure there is one and only one path from any point to any other point. Computer science uses tree structures extensively (see Tree (data structure) and telecommunications.)
Example of a radial tree, from a 1924 organization chart that emphasizes a central authority [1] A radial tree, or radial map, is a method of displaying a tree structure (e.g., a tree data structure) in a way that expands outwards, radially. It is one of many ways to visually display a tree, [2] [3] with examples dating back to the early 20th ...
The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database. [citation needed] These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language.
The SQL/Schemata, or Information and Definition Schemas, part of the SQL standard is defined by ISO/IEC 9075-11:2008. SQL/Schemata defines the information schema and definition schema , providing a common set of tools to make SQL databases and objects self-describing.