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Queen's University Library

QCAT: Use Boolean Operators

What are Boolean operators? George Boole was an English mathematician. He invented a method of symbolically representing relationships between sets using the operators AND, OR, and NOT.

Why are these operators important? When you type words into a library index, you need to connect them according to the rules for that index. Many indexes require the use of Boolean operators to express your search words in a form that the computer can interpret.

OPERATOR EXAMPLE
AND
  • use to connect words and phrases and to narrow search results

    e.g. television and violence and children
    e.g. globalization and "developing countries"
[Boolean Logic AND]
OR
  • use to search all words and to broaden search results

    e.g. "greenhouse effect" or ozone
  • use brackets for grouping terms that are connected with "or"

    e.g. ("acid rain" or pollution) and "wild life" and ontario
[Boolean Logic OR]
NOT
  • use with caution to exclude words from search and to narrow results
    e.g. Chaucer not prologue

    e.g. sports and drugs not steroids
[Boolean Logic NOT]

Last Updated: 22 November 2010