Database Management Systems (DBMS) |
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Covers operation symbols used for math, string manipulation, logic, and comparison expressions. Includes order of precedence and truth table. Math, Comparison, and Logical Operator SymbolsMath Operator SymbolsMath operator symbols indicate what operations are to be performed when evaluating an arithmetic expression such as X / Y * (A + B * A). Symbols
Order of PrecedenceWhen evaluating a mathematical or logical expression, expressions contained within parenthesis are always evaluated first. The order of precedence for the remaining math operators is from left to right in the following order:
The following phrase is useful to remember the order of precedence
for the mathematical operators. Just be sure to realize that multiplication
does not come before division (they are equal and performed left to
right unless there are parenthesis) and addition does not come
before subtraction (they are equal and performed left to right unless there
are parenthesis).
String operation symbolsString operation symbols indicate how two or more character strings
are combined, an operation known as concatenation.
Example (_'s represent blank spaces)
Comparison operator symbolsComparison operators are used to make comparisons between math,
character, or date expressions. They result in the logical values
True or False, as used with boolean logic.
Logical operator symbolsLogical operators (sometimes called Boolean operators) are used in
logical (or Boolean) expressions. (Example: (A .AND. B .OR. C) ).
Just as in mathematical expressions, there is a specific order of precedence for evaluating logical expressions which have more than two operators. Expressions inside of parentheses are evaluated first, and the logical operators are evaluated in the following order:
Example: the parentheses in the following example make the two statements logically different:
Truth TableThe following Truth Table provides all the rules needed to evaluate
logical expressions.
The AND and OR columns of a truth table can be summarized as follows:
Bruce Miller, 2005 |