Boolean operators are the most essential tool in a researcher’s toolkit. These words: AND, OR, and NOT, allow a researcher to narrow or broaden their search by instructing the database how to connect your search terms.
Using AND narrows your search results. When placed between two keywords, the AND tells the database you only want to see articles that contain both keywords. For example, look at the following search:
This search will only show articles that reference the budget deficit in the United States. The AND ensures you find articles that match your topic as closely as possible. You can also add more keywords to be more specific:
When using the AND make sure to be specific enough to find relevant articles, but not too specific where you’re unable to find enough for your assignment.
The OR broadens search results. While the AND looks for articles that have all of the keywords, the OR tells the database to find at least one of them. Look at the following example:
The OR tells the database to find articles that mention heart attacks, as well as articles that mention myocardial infarctions. This search will find articles that use either the common or medical term for the same idea.
The NOT removes articles from search results. As an example, let’s say you need research about special education in a foreign country. Run a search for special education and you’ll find that most of the articles in your search results focus on special education in the United States. However, if we conduct the following search:
This search will look for articles on special education, but will remove any that reference the United States. What is left is a series of articles focused on special education issues in countries from all over the world.
Using Boolean logic is essential to locating the best sources, but it is often a process of trial and error. If the initial search doesn’t have a lot of useful sources, don’t give up! Try different combinations of keywords and Boolean logic until you find a search that works.
Nesting is when you surround parts of your search query with parentheses. This is done to tell the database’s search engine which part of your search to perform first. Many, though not all, databases allow this technique.
Example: (human AND rights) AND NGOs
The most useful application of nesting is to list synonyms within parentheses using the Boolean operator OR, and combine these in a search with other concepts.
Example: (therapy OR treatments) AND schizophrenia