Try the new interactive guide for immediate step-by-step help with creating a search phrase for health sciences databases:
Use Boolean operators (the words AND, OR, and NOT) to combine your search terms.
You can use as many Boolean operators as you like in a search phrase, but include related concepts in parentheses to keep the phrase organized (this is called nesting). For example:
For more information and practice exercises, see the Boolean searching guide by the Colorado State University Libraries or view the "Boolean Operators: Pirates vs. Ninjas" video.
Use quotation marks (“ ”) around phrases to keep words together. For example, a search for tumor marker in PubMed will retrieve both of the articles below. A search for “tumor marker” will retrieve only the second article.
Note: in some databases, you cannot use quotations marks and asterisks together. See the box below, "Asterisks to 'Fill-in-the-Blank,'" for examples.
Use asterisks (*) to “fill-in-the-blank” at the end of a word (this is called truncation). The asterisk will be replaced by any applicable letters. (You can use asterisks as a shortcut for OR-ing words that have identical roots.)
For example, therap* will search for therapy, therapies, therapist, therapists, therapeutic, etc.
Be careful where you place the asterisk. A search for car* as a “shortcut” for cardiac, cardiology, etc. will also retrieve items on carcinogenesis, car safety, and Caraboose the tooth fairy moose.
Note: in some databases, you cannot use quotations marks and asterisks together. For example:
Let’s say you are conducting a search in Imaginary Health Database on the role of antioxidants in heart disease.
Note: don't be alarmed by the length of the search phrases below. Because this is an all-inclusive example, the final search phrase is much more complex than you will normally use in your research.
Attempt 1 - AND: Identify your keywords and combine them with AND.
Since you want articles about both of these topics, use AND in your search. You can use truncation (*) to search for both the singular and plural forms of a keyword.
Antioxidant* AND "Heart Disease"
10 results in Imaginary Health Database
You want more than just 10 results, so you decide to add a few terms and see if they will help you retrieve more citations.
Attempt 2 - AND + OR: Identify related keywords and add them with OR.
Since you would be happy with articles about any of these topics, now you can start using OR in your search. Use parentheses to keep the related keywords together.
(Antioxidant* OR "Vitamin A" OR "Vitamin C") AND ("Heart Disease" OR "Cardiac Disease" OR Cardiomyopathy)
50 results in Imaginary Health Database
Now you have many results, but you notice a lot of them are about diabetes, which you don’t want.
Attempt 3 - AND + OR + NOT: Identify unwanted keywords and add them with NOT.
Time to use NOT for those unwanted terms (and, yes, you can use double or even triple parentheses to keep things neat):
((Antioxidant* OR "Vitamin A" OR "Vitamin C") AND ("Heart Disease" OR "Cardiac Disease" OR Cardiomyopathy)) NOT (Diabetes OR Hyperglycemia)
30 results in Imaginary Health Database
Just right! Your final search phrase looks like this: