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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 ).
Operators that are in the same cell (there may be several rows of operators listed in a cell) are grouped with the same precedence, in the given direction. An operator's precedence is unaffected by overloading. The syntax of expressions in C and C++ is specified by a phrase structure grammar. [7] The table given here has been inferred from the ...
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
The semantics of operators particularly depends on value, evaluation strategy, and argument passing mode (such as Boolean short-circuiting). Simply, an expression involving an operator is evaluated in some way, and the resulting value may be just a value (an r-value), or may be an object allowing assignment (an l-value).
Other languages use different symbols for the two operators. [22] For example: In ALGOL and Pascal, the assignment operator is a colon and an equals sign (":=") while the equality operator is a single equals ("="). In C, the assignment operator is a single equals sign ("=") while the equality operator is a pair of equals signs ("==").
Conjunctive queries also correspond to select-project-join queries in relational algebra (i.e., relational algebra queries that do not use the operations union or difference) and to select-from-where queries in SQL in which the where-condition uses exclusively conjunctions of atomic equality conditions, i.e. conditions constructed from column ...
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APL uses the term operator in Heaviside’s sense as a moderator of a function as opposed to some other programming language's use of the same term as something that operates on data, ref. relational operator and operators generally.