To return the results you want you need to combine your keywords in a specific way. To achieve this, Boolean operators are used to combine search terms together to help focus a search and find relevant search terms. There are two main Boolean operators
Use AND to combine different concepts together and narrow results.
When terms are combined with AND the results will have all terms.
Be careful about having too many concepts combined with AND as you may end up with zero results.
However, if you have too many results add another term with AND. This will be covered more in the section about updating your search.
For example, if were searching for articles about treating pain in migraines without drugs. We would want all the terms to appear in our search. So the search would look like this
pain AND migraines AND non-drugs
Use OR to combine similar keywords together to broaden your search results, as when terms are combined with OR the results will have one or more of the terms. The more keywords you join with OR, the more records you will retrieve.
While you can have multiple concepts combined with OR, be careful to use only words that make sense for your topic. Also, avoid going too broad as this will increase your results to much.
For example, if were searching for articles about treating pain in migraines without drugs.
We could expand the concept of without drugs and look at specific examples of non-drug treatment such as cognitive behavioral therapy or acupuncture
cognitive behavioral therapy OR acupuncture
Below you can see how the Boolean operators are used. Note: Capitalize your operators as a matter of practice. In some platforms it does not matter but others it does.
When you have a complicated research question, mixing multiple Boolean Operators in one search string can be helpful.
However, there is a specific method for combining these terms. While it is important to understand how these terms should be combined, the best error-free method is to (see the example below) by entering each group of keywords in its own box in the search.
For a database to understand how you want your search terms combined, you need to use parentheses ( ) to separate keywords when using the OR AND operators.
For example,
With the use of parentheses ( ) in this research questions pain AND migraines AND (CBT OR acupuncture OR relaxation) the database will retrieve records containing:
Without the use of parentheses ( ) in this research questions pain AND migraines AND CBT OR acupuncture OR relaxation the database will retrieve records containing:
This is because the AND will be done first, followed by anything after an OR.
Other Notes
You can use multiple parentheses ( ) around each set of keywords using OR, for example:
The order of the terms in the search string or brackets does not matter. All of the terms are treated equally. You do not need to put your terms in order of importance.
Try the exercise below to get some more practice with building search strings
Look at the synonyms or special characters page or move to the page about initial searching.
