NexusDB V3 Manual

Boolean Value Expressions

Specify a boolean value.

Syntax

<boolean value expression> ::=

<boolean term> ::=

<boolean factor> ::= [ NOT ] <boolean test>

<boolean test> ::= <boolean primary> [ IS [ NOT ] <truth value> ]

<truth value> ::=

<boolean primary> ::=

<boolean predicand> ::=

Notes

      <boolean primary> IS NOT <truth value>

is equivalent to:

      NOT <boolean primary> IS <truth value>

Truth tables

Since SQL supports null values and predicates whose value can be UNKNOWN, a three-valued logic is used to evaluate boolean value expressions. The rules of this logic are summarized in the following tables:

Truth Table for the AND Boolean Operator

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Truth Table for the OR Boolean Operator

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Truth Table for the NOT Boolean Operator

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Truth Table for the IS Boolean Operator

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Examples

      SELECT studentID, studentName, city, state

      FROM students

      WHERE  city = 'Newport' AND state = 'CA'

      SELECT studentID, studentName, city, state

      FROM students

      WHERE  city = 'Newport' AND ( state = 'CA' OR state = 'RI' )

      SELECT studentID, studentName, city, state

      FROM students

      WHERE  ( city = 'Newport' AND state = 'CA' ) OR state = 'MA'

      SELECT studentID, studentName, city, state

      FROM students

      WHERE  NOT ( ( city = 'Boston' AND state = 'MA' ) OR state = 'CA' )

Conformance