When two different Boolean commands are used in the same search statement, parentheses must be included to indicate the order in which they are to be executed. Words enclosed in parentheses are searched first: The left phrase in parentheses is searched first; then, based upon those results, the second phrase in parentheses is searched.This technique is called nesting. Nesting is often used to "mark off" separate concepts by grouping together synonyms or related terms connected with OR. Nesting also provides a clear visual structure useful in developing, analyzing and modifying your search.
Ex. (osteoarthritis or degenerative joint disease) and (pain--therapy or relief of pain)
In the above example, parentheses mark off Concept #1 (osteoarthritis) and Concept #2 (relief of pain). For Concept #1, degenerative joint disease is joined as a related concept/synonym with osteoarthritis, using the connector OR. For Concept #2, the CINAHL official heading "pain--therapy" is joined with the key phrase "relief of pain") using OR. For comprehensive searches, more terms can be added as necessary.
The following search statement is now ready to be copied or typed into a database search box:
(osteoarthritis or degenerative joint disease) and (pain--therapy or relief of pain)
Other examples of nesting:
