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Research Guides

Boolean Searching: Boolean Searching

What is Boolean Logic?

What is Boolean Logic? 

Boolean logic is a way of organizing and combining sets to get desired results.  In information searching, using Boolean logic can help you combine search terms in efficient ways to get more relevant results in one search.

Why is it important?

Databases and library catalogs are built with specific structure.  Boolean operators allow you to narrow your searches to find better results in less time.  Even Google uses Boolean operators.

Boolean logic searching uses AND, OR, NOT as "operators" or words that combine terms in certain ways.  Below are examples of how AND, OR and NOT work,  either narrowing or expanding your results.



You are thinking of adopting a dog, specifically a pit bull.  However you remember staffordshire terrier is another breed name often used for pit bulls in the United States by humane societies.  If you were searching for such a dog, you would want to structure your search to include all results from both terms by using OR.

example image using Boolean operator OR


Before adopting your pit bull, you are interested in the training option and types of training available.  A great way to search for information that only includes both terms is by using AND.  

example image using Boolean operator AND


During your searches, you notice results are appearing for the term pit bull that do not relate to the animal (e.g. Pitbull the rapper).  To exclude a certain aspect of a term from your search results, use NOT.

example image using Boolean operator NOT

Pit bull image: taken from flickr, labeled for reuse

Stafforshire Terrier image: taken from flickr, labeled for reuse

Pitbull (rapper) image: taken from flickr, labeled for reuse

Boolean Tutorials

These tutorials were developed by Colorado State University.

Boolean Operators

Commonly Used Boolean Operators

What are Boolean Operators?

Boolean operators are used in search engines in databases and on the web to define relationships between words and groups of words.  They can help you refine your search to find the best possible results. 

AND Use AND to retrieve both search terms
OR Use OR to retrieve either search term(s)
NOT Use NOT to exclude search term(s)
" " Use " " to keep the order of words intact
( ) Use ( ) to phrase search; this organizes the order of relationships in your search
* Use * to the end of a term to search all ending of the root word, e.g. govern* retrieves government, government, govern, governs, governor 
? Use ? to find alternate spellings, e.g. wom?n retrieves woman or women 

Tips for searching within search engines:

  • Searching is not case sensitive
  • Most search engines do not search punctuation or certain words, e.g. the, a, of, by
Visit Boolean Searching for more information.