Boolean operators (also called connectors) allow you to specify how you would like a database search platform to handle the terms of your search.
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.
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 |
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").
Search Query: | Number of Results Returned: |
---|---|
telehealth | 6,100 |
telehealth OR telemedicine | 33,000 |
telehealth OR telemedicine OR mobile application | 51,000 |
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.
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.
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.
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 |