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Search Library Databases Effectively: Searching with Boolean Terms

Boolean Operator Basics

Boolean operators connect your search terms to either narrow or broaden your search results. You should use them to focus a search, particularly when your topic contains multiple search terms. Commonly used Boolean operators are: AND, OR, and NOT.

Practical Boolean Application

Venn diagram. Burger and Fries, center highlighted

Burger AND Fries

Search results will contain both burger and fries. Using AND returns all search words.

Venn diagram. Burger or Fries, all highlighted.

Burger OR Fries

Search results will contain either burger, fries, or both. Using OR returns any of the search words.

Venn diagram. Burger not Fries only burger colored

Burger NOT Fries

Search results will contain burger but not fries. Using NOT ensures that the term that follows NOT will not appear in search results.

Combining Multiple Terms

Unlike Google, a database does not assume what and how you want to search.  It only returns results based on how you have used the search commands ( AND, OR, NOT).  Therefore, it is important to know the logical order in which you connect your search terms. 

Can you use multiple connectors or a combination of AND and OR operators in a single search string?

  • Absolutely! However, remember that databases connect search concepts with AND first.

How does this work?

  • For example, you are looking for articles on diabetes in obese population. 
  • You know that you can use alternate search terms for "obese population" to expand your search results. 
  • You type: diabetes AND obesity OR overweight. How does a database interpret this search string?
    • It will first search for diabetes AND obesity, It will then combine that search result with "OR overweight". This is not what you want!

How do you avoid that?

  • Try using parentheses around your similar search terms: Diabetes AND ( obesity OR overweight) 

Try It

"Try It!" with blank notebook and pencil

Watch this tutorial to learn simple search strategies.

Learn More

Pencils against a blue background. 'Learn More'

Click on the link below and move your cursor over the search operators-AND, OR, NOT- to see how each one works.

More Research Skills Guides

Want to learn more? View our other research skills guides:

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