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MPH Research Guidance for Writing Papers: Searching Techniques

Last Updated: Feb 21, 2024 10:23 AM

Boolean Searching

Boolean logic uses the words AND, OR, NOT as a way to connect different search concepts to get you the results you need.


  • Requires ALL concepts to be present in your results
  • Will return you fewer, but more relevant results
  • In some databases, the AND is assumed (e.g.Google)

Venn diagram of Boolean AND depicting search terms e-cigarettes AND lung cancer


In this example, you would only get articles about both e-cigarettes and lung cancer, represented here by the area in the middle.  


  • Requires ANY of the concepts in your search to be present
  • Broadens your results
  • Usually must be selected or typed out (e.g. Google – use OR)

Venn diagram of Boolean OR depicting search terms e-cigarettes OR vaping

In this example you would get articles that discussed either e-cigarettes or vaping, but not necessarily in the same article.


  • Excludes words from your search
  • Will return you fewer results
  • Is usually used when you are retrieving articles about other concepts that are implied by your search terms or that are out of context for your search (e.g. electric stimulation NOT diagnosis would exclude articles discussing electric stimulation as a diagnostic tool)
  • In some databases, is represented by the “-” (e.g. Google)

Venn diagram of Boolean NOT depicting search terms tobacco smoking NOT lung cancer

In this example, you would get only get articles dealing with tobacco addiction (the area represented by green).


Nesting (aka "Order of Operations)

If you have more than 2 terms and are using more than 1 Boolean connector, you need to be careful about the order in which you search. Use parentheses if you need to use multiple connectors.

For example:

lung cancer AND (e-cigarettes OR vaping)

Truncation and Wildcards

Truncation allows you to search for the root of a term to include plurals and variants.

  • Broadens your search
  • The symbols vary by database – check the help section if you are unsure
    • PubMed & Ovid use: *
    • Ovid uses: $

For example: alcoh* would retrieve: alcohol, alcohols, alcoholic, alcoholics, alcoholism

Wildcards allow you to broaden your search by replacing one letter with a symbol

  • The symbols vary by database – check the help sections if you are unsure

For example: orthop#dic would retrieve: orthopedic or orthopaedic


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