Boolean operator

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The Boolean searching operators are: AND OR NOT. They are used to combine keywords to form a more precise search query. (Early search engines required them to be expressed in all-caps.)

  • "Cats AND Dogs" will obtain only records that contain both words
  • "Cats OR Dogs" will obtain all records that contain either word
  • "Cats NOT Dogs" will obtain records that contain cats, minus those that contain dogs

Boolean searching is a method of combining concepts in keywords search which allows the searcher to use three logical commands (sometimes called operators).

The OR command is used to expand or broaden search results by including synonyms and related terms.

  • Search statement: violence or conflict or aggression

The AND command is used to narrow search results. Each time another concept is added using and the search becomes more specific. In some online catalogs, and electronic databases, the and command is implicit -- there is no need to type it in a keywords search.

  • Search statement: violence and television
  • Or just: violence television

The NOT command is used to exclude unwanted records from search results.

  • Search statement: television not video

When two different Boolean commands are used in the same search statement, parentheses must be included to indicate which command is to be performed first (syntax).

  • 'Search statement: television and (violence or aggression)
  • Or just: television (violence or aggression)

See also: fuzzy search, truncation, and nesting.

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