Boolean Operators
Much of searching involves more than one keyword. If you have two or more search terms, you need to "tell" the search engine or database how those terms are related. Boolean operators allow you to state that relationship. They can help you narrow, broaden, or refine your search.
AND
You can narrow your search by using the AND operator. It is most useful when you are receiving too many results on your topic.
Let's say that you are looking for information on dogs because you want
to get one as a pet. If you just search for "dogs," your results will
include any items that mention the word, such as materials on the movie
Reservoir Dogs.
To narrow your search, you can type in "dogs AND pets." Now the
materials have to mention both words to show up in your results list,
so it is much more likely that any item talks about dogs in relation to
having pets.
OR
You can broaden your search by using the OR operator. It will return results that use any one of your search terms. It is most useful when materials use several terms to talk about the same topic.
If you want to get a dog, but you are still deciding on the breed, then
you can perform one search to research more than one breed at a time.
For example, you might be trying to choose between a collie and a
retriever. You can search for "collie OR retriever" to get information
on either breed in your results list.
NOT
If the results you are getting include way too many irrelevant items, you can refine your search by using the NOT operator. The term that comes after that operator will be excluded from your search results.
For instance, if you actually want a terrier for a pet, you might want
to find information on the different types of terriers, but you know
that you don't want to get a bull terrier. To exclude that breed from
your search, you can phrase your search as "terrier NOT bull." Your
results will include information on all other terriers, but not on bull
terriers.
For More Information...
The 3 operators introduced above are the most common ones, but Boolean logic uses other operators as well. To get more advanced tips on searching with Boolean logic, you can use any of the tutorials below:
- Electronic Searching from Duke Libraries
- Searching with Boolean Logic and Proximity Operators from USC Beaufort Library
- Boolean Operators Chart from World LII
Also, be sure to check the help pages of the database or search engine that you are using to find more detailed information on how it handles Boolean logic.
This page was written by Mariela Hristova in Spring 2005.
This page was reviewed by John Reid in Spring 2006.
This page was reviewed by Lisa Charbonnet in Spring 2007.
INF 382S: Library Instruction and Information Literacy, taught by Dr. Loriene Roy
School of Information,
The University of Texas at Austin