Conducting a Boolean Search Conducting a Boolean Search A Boolean expression is a complex query that uses Boolean operators to combine keywords. The Boolean operators set the conditions for a search.
Boolean operators are most useful when combined to produce a more complex, specific query.
Use brackets to group parts of the Boolean expression together that must be evaluated first. If you don't use brackets, the keywords combined by the AND operator will be evaluated first. If you don't use brackets, the keywords combined by the OR operator will be evaluated last. You cannot use the AND NOT operator before bracketed terms. This is invalid.