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Alabama Virtual Library Overview: Boolean Operators

 

Technique 1: Boolean Operators

Boolean operators are one of the most powerful ways to expand or limit a search. Operators can be selected using the drop downs next to the search bar on both EBSCO and Gale's advanced search screens.

EBSCO Advanced Search

Gale Advanced Search

The three basic operators and their functions are:

  • AND tells the database to include results that have all of the terms and is used to narrow search results. Searching "Heart" will call up more results than "Heart AND Lung".
  • OR tells the database to include results that have any of the terms and is used to expand search results. Searching "Heart OR Lung" will call up more results than "Heart AND Lung" because the databases will include instances where either word is present and where both words are present.
  • NOT tells the database to exclude results with a certain word and is used to narrow search results. In our example using the words heart and lung, searching "Heart AND Lung NOT Smoking" will exclude results that have the word smoking in them.

A good rule of thumb is: if you have too many search results, apply AND to your search phrase to connect various pieces of information to hone in on the information you are looking for; if you get to few results, apply OR to your search phrase to connect two or more concepts to broaden your search results; and if you have too many results that contain irrelevant information, apply NOT to your search phrase to exclude specific words or concepts, which will filter out the information you don't want and make it easier to find the information you do want.