Skip to Main Content

Holiday Schedule: JPS Medical Library staff follow the UNTHSC holiday schedule.
We will be unavailable starting Dec. 20 at 12Noon and return Jan. 2.
UpToDate: New to JPS Health Network? Create an UpToDate account

Home > Research > Resources by Topic > Literature Searching

Literature Searching

A guide to help you navigate the literature searching process.

Boolean Operators

What is a database?

The short answer: A collection of information organized so that it is searchable and retrievable.

Academic databases (such as PubMed, CINAHL, and PsycINFO) collect information about journal articles, book chapters, conference proceedings, dissertations, and much more in a particular area of scholarship. This information is then made to be easily searchable by you, the user.

Think of library databases as buckets and each bucket is filled with journals. Looking in multiple buckets offers more journal coverage. No single bucket will have all the information you need.

The library subscribes to databases that provide coverage in areas relevant to the health sciences. No single database will hold all of the information needed for research, so it's important to search in more than one. Together, databases and indexing make finding scholarly articles possible.

What does Indexing mean?

Journal articles and other material in databases are indexed with subject terms which make them searchable. Think of hashtags and social media. When a hashtag is used it connects all photos or posts with that same hashtag. Articles within databases have indexing terms attached to them connecting articles with similar themes. Once that term is input in a search bar it will bring up articles with the same or similar indexing terms. Medical Subject Headings (MeSH) in PubMed are an example of indexing terms.

What are Boolean Operators?

Boolean operators are used to pull search terms together. They allow you to connect key terms in a format that is searchable in a database. The most common Boolean Operators are AND, OR, and NOT.

AND

AND will narrow the search. It requires all terms connected by AND to be included in the search results. The example below reflects a search that requires both "diabetes AND nutrition" to be in the results.

Boolean AND Operator

OR

OR will expand the search. It allows for either term to be present in the search results. It is used for connecting synonyms of search topic key terms. The example below reflects a search that requires either "medication OR prescription" to be included in the results. It does not require both.

Boolean OR Operator

NOT

NOT is used to exclude terms from the search. Use caution when using NOT, as it may weed out items are relevant to the topic. The example below reflects a search that includes "smoking cessation" but does not include any articles that also talk about "pregnancy."

Boolean NOT Operator

Quotation Marks

There may be instances when searching which require results with a very specific term or phrase. When looking for an exact phrase or word, placing quotation marks on either side will prompt the database to search for the words in exactly the order they appear.

For example: "food desert"

By placing quotation marks on either side the database knows to look for those terms together, not separately in the article.

How Do I Connect Boolean Operators Together?

Sometimes, when you have a complicated research question, using multiple Boolean Operators in one search string can be helpful. In these instances, connecting different parts of the search string together using parentheses will help (it will resemble a simple math equation). Let's connect the first two examples above:

Example: (diabetes AND nutrition) AND (medication OR prescription)

In this example, the system will first look for articles containing "diabetes AND nutrition." It will then look through the results for articles that contain "medication OR prescription." So, we will only get results that have to do with medication as it relates to the nutrition of diabetic patients.

If we did not use parentheses, our search string would look like this:

Incorrect Example: diabetes AND nutrition AND medication OR prescription

Do you see the difference? In the incorrect example, the system will look for articles that contain "diabetes AND nutrition AND medication," as well as ALL the entries in the database that contain "prescription," whether or not they have anything to do with the first part of the search.

How Do I Filter Search Results?

Most databases will have filtering options built in to the search page that can help narrow down your search results.  Options for filters can include any of the following: Date, Language, Age, Article Type, Location, etc.

Each database will present different options, but they can really help refine your search and make it more specific. (Think filtering by size or color when online shopping).