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Composing a Search: Boolean Logic

Interactive Guide to demonstrate how to compose a search and test it on a sample of library databases.

Boolean Logic

Boolean Logic is the application of AND, OR and NOT operators to a search to improve its precision.

It is named after the 19th century mathematician George Boole.


The AND operator will

  • require that all the terms must be in each of the search results
  • narrow the search returning fewer results


The OR operator will

  • require that at least one of the terms must be in each of the search results
  • broaden the search returning more results



The NOT operator will

  • require that the term must not be included in the search results
  • narrow the search returning fewer results

Use this operator with caution as it may eliminate relevant results.  For example, if  a search on substance abuse includes "NOT alcohol" and, an author states that, "this paper will not discuss alcohol abuse", the paper may be eliminated from the search results.  It includes the word alcohol but discusses the abuse of other substances.

The Matrix

It is a good idea to enter your key terms and synonyms into a simple table.

Consider the research topic "In Western Australia, adolescents have not got the message, drugs, other than alcohol, and driving do not mix."

Key terms drugs driving adolescents "western australia" alcohol
Synonym "prohibited substance*"   teenagers "western australian" liquor
Synonym     youth wa  

Join each of the terms in a column with the OR operator.  Add parentheses to make sure that these operators are processed first.

(drugs OR "prohibited substance*")


(adolescents OR teenagers OR youth)

("western australia" OR "western australian OR WA)

(alcohol OR liquor)

Finally, join each of the columns with AND or NOT operators

(drugs OR "prohibited substance*") AND driving AND (adolescents OR teenagers OR youth) AND ("western australia" OR "western australian OR WA) NOT (alcohol OR liquor)


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