Search Library Databases Effectively: Searching with Boolean Terms

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.

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) 

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