Behind every search in a database or even in Google, there are mathematical operations occurring. While it is not necessary to understand the complex mathematics behind searching, understanding the basic mechanics of the formulas can help you understand how to construct a search. Just like basic mathematics, searching utilizes operators. Instead of [+ - × or ÷], the operators for database searching are: AND, OR, and NOT, known as Boolean operators.
AND combines search terms to retrieve articles that use the major concepts of a search, identified in the PICO(T) process.
The Venn Diagram below represents the use of AND to combine the terms ‘nurse burnout’ and ‘patient satisfaction’. The gray area where the two circles overlap represents the AND as well as the set of articles that the search would retrieve: articles that discuss both nurse burnout and patient satisfaction.
Nurse burnout AND Patient satisfaction
OR combines search terms to retrieve articles that use any of the terms that describe a concept or set of concepts or groups you are interested in.
When would I use OR?
OR is important if:
In the Venn Diagram below, the gray area shows that the use of OR gathers all articles that discuss football, hockey or soccer.
Football OR Hockey OR Soccer
NOT excludes terms from the set of search results. The use of NOT is generally discouraged, since it can unintentionally exclude relevant articles from your results.
In use, it is represented by the Venn Diagram below, in which the area between ‘sepsis’ and ‘burn’ represents the NOT—in this example, the articles retrieved on the subject ‘sepsis’ would not include articles that discuss sepsis in burns.
Sepsis NOT Burn
In actual usage, searches often involve a combination of AND and OR, which may require the use of parentheses. The parentheses preserve the order of operations (remember your algebra!). The words combined with OR live within the parentheses.
E.g. (elderly OR aged OR geriatric)
The concepts from PICO(T) may involve one or several groups of synonyms or alternative concepts. The groups are placed in parentheses, then combined with an AND:
E.g. (elderly OR aged OR geriatric) AND (sleep disturbance OR insomnia OR sleep disorder) AND inpatient
In the database, the parentheses here result in a FOIL operation, so that the search will retrieve articles containing the terms: