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Library Research Tips

Introduction to Boolean Operators

Boolean Operators are words that connect keywords (search terms) together to broaden or narrow the results retrieved. In library research they are often used with the library's research databases or the library catalog. 

The three Boolean operators are AND, OR, and NOT.

  • AND narrows your search results by limiting your results to those that contain both words connected with AND.
  • OR expands your search results by including results that contain one word, the other word, or both words.
  • NOT narrows your search results by limiting your results to those that contain the word you designate before NOT, but not the word after NOT.

One way to visualize Boolean Operators is to use a Venn diagram. See below or watch the video to the right.

Boolean Operator Venn Diagram indcating how a search of Peanut Butter and Jelly changes your results based on the boolean operator used to combine them. AND shades only the middle of the diagram, indicating any results would only have peanut butter and jelly in them. OR indicates that every result with peanut butter, with jelly, and with peanut butter and jelly would appear. Searching for Peanut Butter NOT Jelly indicates that only peanut butter would appear.

Boolean Operators

Boolean Operators in Academic Search Complete

Take a look at the following sandwich related searches in Academic Search Complete to see how this affects the number of search results generated.

Diagram indicating how number of search results change depending on boolean operator used. A search for just peanut butter returns 7034 in a database. A search for just Jelly returns 5182 results. A search for peanut butter AND Jelly returns 181 results. A search for peanut butter OR jelly returns 12035 results. A search for peanut butter NOT jelly returns 6853 results.