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Health (Nursing, Medicine, Allied Health): Boolean Searching

Guide to research sources and tools for locating health evidence in books, journals, databases.

Boolean Operators: The Basics

Boolean operators (also called connectors) allow you to specify how you would like a database search platform to handle the terms of your search.  

AND

Connecting search terms with AND tells the database to return records only if all those terms appear in the record.  Connecting additional terms with AND creates a narrower search, as there will be a smaller number of records that contain the required terms.

Example database search query using the Boolean operator AND
Search Query: Number of Results Returned:
type II diabetes 166,000
type II diabetes AND telehealth 556
type II diabetes AND telehealth AND blood glucose 195

OR

Connecting search terms with OR tells the database to return records if any of the given terms appear in the record.  Connecting synonyms and alternate terms with OR expands the search results ("OR retrieves MORE").

Example database search query using the Boolean operator OR
Search Query: Number of Results Returned:
telehealth 6,100
telehealth OR telemedicine 33,000
telehealth OR telemedicine OR mobile application 51,000

NOT*

Connecting search terms with NOT tells the database to exclude any records that contain the specified term.  Adding an excluded term with NOT will create a narrower, more specific search. 

Example database search query using the Boolean operator NOT
Search Query: Number of Results Returned:
telemedicine 36,000
telemedicine NOT video 33,000

*Caution: use the NOT operator sparingly and carefully; you could accidentally exclude records that are actually relevant to your search.  For instance, in the example above, even if you aren't interested in seeing articles that talk about video-based telemedicine interventions, if you restrict that word completely, you will miss articles just because they contain the word 'video' somewhere in the abstract.    


Complex Searching

A complex search can be built by using the AND and OR operators together.  Separate concepts can be connected with AND, while synonyms for those concepts can be connected with OR.  It is important to note that synonymous terms connected with OR should be nested within parentheses, so that the database understands to keep those terms together as a set.  

Example complex database search query using multiple Boolean operators
Search Query: Number of Results Returned:
type II diabetes 166,000
type II diabetes AND telehealth 556
type II diabetes AND (telehealth OR telemedicine OR mobile application) 700

YouTube: Falls AND Exercise (2 min.)

Do exercise programs reduce the incidence of accidental falls in the aged population?