(Boolean operators “logically” compare while numeric operators “arithmetically” compare.)īoolean AND and OR are “binary” - that is to say they operate on two arguments, while NOT is “unary” - operating on one argument. IFīoolean operators - AND, OR, and NOT - operate on boolean values. This is how conditional statements work the arithmetic comparison is done and the execution branch is chosen based on the resulting truth value. For example, the arithmetic comparison ( 3 > 2 ) - three is greater than two - returns a boolean false. Boolean Values Returned From Comparisonsīoolean values are all around, even when not explicitly declared as variables. Your database will probably display Boolean values consistently in only one case. The SQL Select operator will return Boolean values: SELECT Happ圜ustomer FROM reality CustomerIDīoolean values are usually case-insensitive, with TRUE, True, and true being synonymous. False here is zero and true is one (or anything non-zero), BOOLEAN Happ圜ustomer Ĭreate a boolean variable with syntax that parallels creating integer variables: CREATE TABLE reality (īoolean values are the keywords true and false : INSERT INTO Early systems provided only number variables, so some databases have their boolean data type as merely an alias for INTEGER. SQL Boolean Variablesĭatabase implementations vary in syntax the Boolean data type is usually written as a BOOL or BOOLEAN. This blog entry will cover the BOOLEAN data type and the AND, OR, and NOT operators. Computing systems need some special way to represent the truth of things. It is false that dinosaurs and humans lived contemporaneously. It is true that a blue whale is bigger than a minnow. Whereas addition and subtraction, for example, operate upon numbers, some aspects of the world deal with the either-or nature of truth. The SQL Boolean algebra operations - AND, OR, NOT - operate on true and false values (in contrast with elementary algebra, which deals with numbers). Relational databases store information in tables - in columns that describe aspects of an item and rows which tie together the columns.
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