Veterinary Medicine

Boolean Operators

Boolean Operators act as an internal formula for databases to know how words and/or phrases are combined or excluded. The most common operators are: AND, OR, and NOT. 

OR Boolean Operator

OR is used when you are combining similar terms to broaden the scope of your search. For example, in PubMed database, "dog" results in 375,906 articles; "dogs" results in 360,801 articles; and "canine" results in 380,295 articles. Combining these terms using OR signals to the database that it does not matter what term for "dog" populates as long as one of them is in the article. When combined using OR, the results are 394,665 articles. Thus, it results in more articles than each individual word, casting a wider net into the database. 

With the image below, any of the words in yellow - so, "cat" and "dog" - will populate articles. You will get articles on cats, on dogs, and on cats or dogs.

AND Boolean Operator

AND is used when you are combining unlike terms to narrow the scope of your research. AND tells the database that you want every non-related term to populate in the article. For example, in PubMed database, the search string for dog - ((dog) OR (dogs)) OR (canine) - and our search string for heartworms - ((((heartworm) OR (heartworms)) OR (dirofilaria)) OR (dirofilariasis)) OR (dirofilaria immitis) - would be combined using AND to signify to the database that we want both a word for dog and a word for heartworm, but that it does not matter which specific word for each term is used. When combined - (((((heartworm) OR (heartworms)) OR (dirofilaria)) OR (dirofilariasis)) OR (dirofilaria immitis)) AND (((dog) OR (dogs)) OR (canine)) - PubMed results in 2,537 articles that must contain one of each of our terms for dog and heartworm.

In the image below, AND means that any article populated using "cat" and "dog" would have to contain both "cat" AND "dog" in order to populate in the results. Articles containing just "cat" or just "dog" would not populate. 

NOT Boolean Operator

NOT is used when you are trying to eliminate a word from your search results. This Boolean Operator is not recommended when conducting a search for systematic reviews, literature reviews, IACUC submissions, etc. as you can unintentionally eliminate papers that would otherwise be useful.

In the image below, NOT is acting as a barrier within the database to signify that articles must contain "cat" but not "dog." However, any articles that talk about both cats and dogs will also be eliminated because the database eliminates any mention of "dog" even if that article also contains "cat."