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BWRIT 135: Research Writing (Harack): Boolean Operators

Boolean Operators

Most databases don't understand the natural language we speak and need help understanding what we're looking to find. For this, they require a special set of conventions, including: Logical or Boolean operators, wildcard and truncation symbols, and nesting. Databases and internet search engines apply these rules differently, so check the HELP files in the database you are using to find out more.

Boolean Logic consists of three logical operators (connectors): AND, OR and NOT

Boolean Operator: AND

  • Finds sources containing two or more ideas
  • The database will only retrieve items containing both words
  • AND narrows your search
  • You can use AND many times in one search
  • Example: electronic AND voting
Boolean AND 



Boolean Operator: OR

  • Use OR when searching for synonyms
  • OR tells the database that the words can be used interchangeably, so it will retrieve items containing either word
  • OR broadens your search to include synonyms and related words
  • You can use OR many times in one search Example: electronic OR internet OR web
Nesting search terms using: parenthesis ( )
  • Make a complex search using both AND and OR by placing parentheses around synonyms so you don't have to repeat searches
  • Nesting saves you time by allowing you to search multiple synonyms at once
  • Example: (electronic OR internet OR web) AND (vote OR voting) - this cuts down on having to do multiple searches for the combinations of keywords

Boolean OR

Boolean Operator: NOT

  • Use NOT when you wish to exclude records from your search results 
  • Example: pets NOT dogs
  • Be careful when using NOT! The term you want may be present in an important way in results that also contain the word you wish to avoid     

Boolean NOT


I used the search phrase tuberculosis and treatment, but I'm getting too many results. If I want to narrow my search adding the term effectiveness, the best Boolean operator to use would be:

AND: 15 votes (68.18%)
OR: 1 votes (4.55%)
NOT: 5 votes (22.73%)
the asterisk: 1 votes (4.55%)
Total Votes: 22

Using different keyword terms for the same idea

I've noticed that different databases seem to use different words for the same idea, like some use "TB," but others use terms like "tuberculosis." If I want to get results using any of those different keyword terms, the best Boolean operator to use would be:

Using different keyword terms for the same idea
AND: 2 votes (11.76%)
OR: 15 votes (88.24%)
NOT: 0 votes (0%)
the asterisk: 0 votes (0%)
Total Votes: 17

Other Search Tools

Truncation: *

  • The * is a common symbol used to replace any number of letters at the ends of words
  • Helps find singulars, plurals, and variant endings of words
  • Check each database's help pages to see which truncation symbol is used in that particular database
  • Example: vot* finds vote, votes, voter, voting, etc.
  • Example: communit* finds community, communities 


  • Most databases let you limit search results. Some limits include:
    • Language  
    • Publication type
    • Date of Publication, etc.

Phrases: " "

  • Enclose phrases in quotation marks when searching the Web or most databases
  • Phrase searching in individual databases may vary. Check the help pages in each database for additional information.
  • Example: "voter registration" 
  • Example: "electoral college"