Education Library Resources: Advanced Searching - Boolean Operators

Boolean operators are words or symbols that help translate your research question into a format academic databases will understand. They can also be used to narrow your search if you're getting too many results, or they can be used to broaden your search if you're getting too few results. Boolean operators are typically written in all-caps because some databases are case-sensitive.

Let's say your research question is "What factors impact college readiness among high school students in the United States?"

Here's how you can break down that question using Boolean operators and search terms.

The OR operator broadens your search. OR is used to join synonyms together. It tells the database you want results that contain any of the search terms specified. Results might contain more than one of the terms specified but they only need to contain one.

There are often multiple ways of describing the same concept. Using synonyms for key concepts ensures you are getting as many relevant results as possible.

The concept college readiness might also be written as college preparedness or college success. The search phrase using OR would be college readiness OR college preparedness OR college success. 

The AND operator narrows your search. AND is used to join multiple concepts together. It tells the database you want results that contain all of the keywords specified.

For the research question What factors impact college readiness among high school students in the United States?, the two main concepts are college readiness and high school students. Using AND, the search string for the database would be college readiness AND high school students.

The NOT operator narrows your search. It tells the database to exclude any results that contain the terms specified. 

For the research question What factors impact college readiness among high school students in the United States?, perhaps we want to exclude any results that focus on international students. The search phrase using NOT would be NOT international students.

Note that you have be extra careful when using NOT because you could accidentally exclude results that may be relevant. The search phrase NOT international students will filter out all results that contain the text international students, even if that phrase is only used in passing (such as, "This study did not focus on international students").

NOT statements are typically added at the very end of a search.

Multiple Boolean operators can be used at the same time. We can combine all three pieces listed above to create one comprehensive search string for the database.

What factors impact college readiness among high school students in the United States?

("college readiness" OR "college prep*" OR "college success") AND "high school student*" NOT "international students"

When concepts with multiple synonyms are joined together, the synonyms (i.e., everything connected with ORs) are sandwiched in parentheses. This is because most databases read search strings with a specific order of operations. This is similar to the PEMDAS order of operations rule in mathematics, where everything inside parentheses is calculated first. AND is processed before NOT in a database, so AND "high school student*" does not need to be in parentheses.

In the search string above, we're telling the database we want results that contain any of the three synonyms for college readiness, and the results also need to contain the exact phrase high school students, but any results that contain the phrase international students need to be filtered out.

Multiple sets of parentheses can be used in the same search string. Consider if we added an additional synonym for high school students.

("college readiness" OR "college prep*" OR "college success") AND ("high school student*" OR "secondary school student*") NOT "international students"

Quotation marks (" ") narrow your search. They force the database to search for the exact text contained within them. These are important because many databases will interpret multi-word search phrases using AND between the words.

For example, the phrase college readiness may be interpreted by the database as college AND readiness. This could produce a lot of unrelated results, such as articles that discuss college students' readiness to enter the workforce. 

Quotes will tell the database you only want results that contain an exact text match for the phrase "college readiness".

Asterisks (*) broaden your search. They tell the database to provide results that contain variations of the specified root term. Most academic databases allow you to use asterisks and quotation marks at the same time.

• "high school student*" will include high school student and high school students

The root does not need to be a full word, but shortening the root too much could produce too many results.

• "college prep*" will include college preparedness, college preparation, college preparatory, and college prep
• "college preparat*" will include college preparation and college preparatory, but not college preparedness or college prep