Boolean Operators are used to connect and define the relationship between your search terms. When searching electronic databases, you can use Boolean operators to either narrow or broaden your results list. The three Boolean operators are AND, OR, and NOT.
Why use Boolean operators?
In the examples below, AND, OR, and NOT are typed in capital letters. This is to emphasize them in the examples. When searching a database, you don't have to capitalize them.
Use AND to:
Use OR to:
You can also use OR to connect two or more similar concepts or search for something which has more than one name.
Use NOT to:
Using NOT can help you further define the parameters of your search by excluding concepts that may often appear together but are not relevant to your research.
You can combine Boolean Operators to search for multiple things at the same time. However, databases follow the commands as they're entered and return results based on those commands, so the order in which you type your search terms is somewhat important.
Databases usually recognize AND as the primary operator, and will connect concepts with AND together first.
If you use a combination of AND and OR operators in a search, enclose the words to be "ORed" together in parentheses.