Introduction to Boolean Logic (continued)

Nesting:

• When using multiple Boolean operators in PubMed, they are processed left to right.

Example: salmonella AND hamburger OR eggs

This will retrieve records that include both terms salmonella AND hamburger as well as all records with the term eggs, whether or not they contain the other two terms.

 

• To change the order in which terms are processed, enclose the terms(s) in parentheses. The terms inside the set of parentheses will be processed as a unit and then incorporated into the overall strategy. This is called nesting.

Example: salmonella AND (hamburger OR eggs)

This will retrieve records that contain the term salmonella, as well as one or both of the terms hamburger OR eggs.