Boolean operators, i.e. AND, OR, NOT are used in most databases. They connect search terms to broaden or narrow search results. Below are examples.
All terms in the search box, excluding the operator, AND, must be present in the retrieved records. The AND operator narrows the search.
Example : violence and evidence-based practice
Any of the terms in the search box may be present in the records when the OR operator is used. OR broadens the search. It can be used for synonyms or variant spellings of a word, also.
Example : elderly or aged
The Boolean operator, NOT, excludes all records found in the search that include the term that follows the operator in the search box. NOT narrows the search.
Example : juvenile delinquency not adult crime
Adapted from the Indiana University IUCAT Help Screens