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General Nursing Research Guide

Boolean Operators and Modifiers (Step Three Continued)

Boolean Operators: 

To search multiple keywords, synonyms or related terms all at once you'll need to use connector terms, also called Boolean Operators.

Using a Boolean Operator will tell the database or catalog to connect the terms together in your search. Boolean operators link together all of your keywords, synonyms and related terms into one long search string. There are three boolean operators: AND, OR, NOT!

 

AND OR NOT

AND combines search terms to retrieve articles. In a research question this will be your keywords. AND narrows your search. For example:

  • breast cancer AND insomnia AND yoga

OR combines all of your synonyms and related keywords. OR will broaden your search. OR is important, because it combines multiple terms. For example:

  • breast cancer OR breast neoplasm OR breast tumor
  • fatigue OR lethargic OR exhaustion

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. NOT will narrow your search. For example:

  • yoga NOT meditation 
  • vegetarian NOT vegan

Modifiers:

In addition to Boolean Operators, modifiers are also used to create an effective search string. A few of the most common modifiers are listed below:

 

  • TRUNCATION

Type an asterisk following a word stem to retrieve a variety of word endings.

Example: searching prevent* retrieves records with the terms prevent, prevents, preventing, prevention, and preventative. Searching mobili* will retrieve records with mobility, mobilization, mobilize.

  • QUOTATIONS

Type quotes around all phrases to ensure that the phrase is searched instead of each word individually: 

Example:  “public health” or '"affordable care act"

  • NESTING

Refers to the use of parentheses to organize a search statement that uses more than one kind of connector or operator (AND, OR, NOT). Nest search terms whenever there's only one text entry box. 

Example: (fatigue OR tiredness) AND (breast cancer OR breast neoplasm).

Boolen Operator and Search String Videos

Putting it All Together: Search String Examples

To create a usable search string, you'll need to combine your boolean operators and modifiers. Remember that AND combines your keywords, and OR combines your synonyms and related terms. When using more than one synonyms or related term you'll need to nest these terms between the boolean operator AND with parenthesis and the operator OR. Let's take a look at a few examples:

 

  • In breast cancer patients experiencing insomnia, what is the effect of yoga on quality of life?

(breast cancer OR breast neoplasm OR breast tumor) AND (insomnia OR sleeplessness OR sleep disorders) AND (yoga OR yoga therapy OR relaxation)

  • In postoperative patients does chlorhexidine bathing reduce the risk of surgical site infections?

(postoperative OR post operative OR post-surgery OR post-surgical) AND chlorhexidine bathing AND (surgical site infection OR surgical wound infection OR postoperative infection) 

  •  In patients with chronic kidney disease does a vegetarian diet compared to a regular diet slow the decline in renal function? 

(chronic kidney disease OR chronic renal failure OR renal insufficiency OR kidney failure) AND (vegetarian OR plant based diet) AND renal function