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Relational algebra is a branch of mathematics that studies the manipulation and analysis of data in relational databases. It defines a set of operations, such as selection, projection, join, and union, that can be applied to relations or sets of tuples. Learn more about the concepts and notation of relational algebra on Wikipedia, including the rename operation that changes the attribute name ...
See also. other types of bullet symbols, listed below. In typography, a bulletor bullet point, •, is a typographical symbol or glyphused to introduce items in a list. For example: • Item 1. • Item 2. • Item 3. The bullet symbol may take any of a variety of shapes, such as circular, square, diamond or arrow.
Wildcard character. In software, a wildcard character is a kind of placeholder represented by a single character, such as an asterisk ( * ), which can be interpreted as a number of literal characters or an empty string. It is often used in file searches so the full name need not be typed. [ 1]
glob (programming) In computer programming, glob ( / ɡlɒb /) patterns specify sets of filenames with wildcard characters. For example, the Unix Bash shell command mv *.txt textfiles/ moves all files with names ending in .txt from the current directory to the directory textfiles. Here, * is a wildcard and *.txt is a glob pattern.
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 .
Relational operator. In computer science, a relational operator is a programming language construct or operator that tests or defines some kind of relation between two entities. These include numerical equality ( e.g., 5 = 5) and inequalities ( e.g., 4 ≥ 3 ). In programming languages that include a distinct boolean data type in their type ...
In high-level computer programming and digital electronics, logical conjunction is commonly represented by an infix operator, usually as a keyword such as "AND", an algebraic multiplication, or the ampersand symbol &(sometimes doubled as in &&). Many languages also provide short-circuitcontrol structures corresponding to logical conjunction.
At sign. The at sign, @, is an accounting and invoice abbreviation meaning "at a rate of" (e.g. 7 widgets @ £ 2 per widget = £14), [ 1] now seen more widely in email addresses and social media platform handles. It is normally read aloud as "at" and is also commonly called the at symbol, commercial at, or address sign .