PubMed Example
Most databases allow you to type Boolean operators right into the search box. Each database is slightly different. Below are some examples from PubMed.
Dengue, malaria and Zika are mosquito-borne illnesses. Searching with AND between these terms returns only articles that mention dengue AND malaria AND Zika. There were 18 articles that referenced all three in the same article.
However, if we search with OR between these terms, we will get articles that reference dengue OR malaria OR Zika. Over 95,000 articles refer to one of these terms.
Where do I use Boolean operators?
As you can see in the example above, Boolean operators (AND, OR and NOT) can be typed into the search box. Another way to conduct a separate search for each of your main concepts, then add them together in Advanced Search.
Example of Everyday Use of Boolean Logic
You have probably used Boolean logic and not realized it. It is a very common way to sort things online. Here's one example: Shoe shopping. Have you ever bought shoes online? The filters off to the left use Boolean logic. Here's how.
- (size) is one concept. Let's say you are looking for shoes that are either (7 OR 7.5)
- (color) is another concept. Let's limit our results to shoes that are (black OR brown)
- (heel height) is another concept. Let's go with (1"-2" OR 2"-3')
We will get shoes that meet the above criteria. If this were spelled out in Boolean logic, it would look like this:
(7 OR 7.5) AND (black OR brown) AND (1"-2" OR 2"-3")
You can play around with this. If you want to limit it to a few brands, you could also add in (Naturalizer OR Clarks). That REDUCES the number of results.
(7 OR 7.5) AND (black OR brown) AND (1"-2" OR 2"-3") AND (Naturalizer OR Clarks)
On the other hand, you can get more results if you add in another OR. Let's say you decide that shoes that are 3"-4" tall are also acceptable. Now you have MORE options to choose from.
(7 OR 7.5) AND (black OR brown) AND (1"-2" OR 2"-3' OR 3"-4")