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History: Database Researching Tips: Boolean Operators

A guide to help both history majors and students enrolled in history courses jump-start their research.

Boolean Overview: 

Before you start typing keywords into a database's search bar, take some time to learn these tricks for searching.  Boolean operators are life-savers when it comes to cutting out miscellaneous resources that don't really meet your criteria. If you start to see the same results over and over, you can manipulate the search using boolean. You have to power to set the boundaries for a search.  Once you know how to use boolean you can apply it toward any database or search engine, even Google! 

Boolean operators are words or "connectors" that, when used between two or more search terms, form the basis of database logic. They help to more clearly define your search parameters by narrowing or broadening the results. 

  • The three basic boolean operators are: ANDOR, and NOT.

Why use Boolean operators?

  • To focus a search, particularly when your topic contains multiple search terms.
  • To connect various pieces of information to find exactly what you're looking for.



  • "Spanish navy" AND "Napoleonic Wars"

​Be aware that in many, but not all, databases, the AND is implied. For example, Google automatically puts an AND in between your search terms. Consequently, though all your search terms are included in the results, they may not be connected together in the way you want.  Google would translate a search for Spanish navy and the Napoleonic wars into:  Spanish AND navy AND  Napoleonic AND Wars. The words may appear individually throughout the resulting records, but not as a phrase.

You can search using phrases simply by using quotation marks. You would translate the above example into "Spanish navy" AND "Napoleonic Wars." This way, the database or search engine knows to only search instances or articles where the words between the quotation marks appear together.


Example: "George Washington" NOT "American Revolution" 

The NOT operator is used to weed out the information you do not want to include in your search.  Let's say you were researching George Washington's biography and you wanted to see results about his presidency or something other than his military service in the American Revolutionary war.  The NOT operator allows you to exclude this phrase and tell the database to ignore the concept.



Example: Jacqueline Kennedy OR Jacqueline Onassis

The OR operator is used to broaden a search by including synonymous terms or subjects that are closely related. Using OR lets the database know that you are interested in seeing articles with both or either of your terms. We as humans know that Jacqueline Kennedy and Jacqueline Onassis are the same person but with different married names. A database won't recognize this, so we must instruct it to search both identities.

Search Order:

It is possible to use more than one boolean operator in the same search, however, it is important to note that the order of terms and operators matters. Just like in math, there is an order of operations. Databases usually recognize AND as the primary operator, and will connect concepts with AND together first.  Therefore, if you use a combination of AND and OR operators in the same search, enclose the OR term in parentheses.


Spies AND (American Revolutionary War OR American War for Independence)