Boolean Operators

With keyword searching, it is possible to perform Boolean searches, that is, to link  terms or phrases using the Boolean operators: AND, OR, and NOT. With these logical operators you can either broaden or narrow a search.

AND narrows a search by combining terms.

The "AND" operator searches for all records which contain both of the words you entered. For example, search for both the keywords
 

These circles show that doing a search on the term "teenagers" brings up 118 records, but only seven of those records, the dark blue area, also have the term "AIDS."

These seven items will be more relevant to someone doing research on teenagers with AIDS than a search of just "teenagers."
 

OR broadens a search by retrieving all items that contain either of the words you entered.

Only one of the terms must be present for a record to be retrieved.

A search for "teenagers OR adolescents" retrieves 178 records, all of the unique items in both circles.

NOT narrows a search by excluding specific terms.

A search for "AIDS NOT teenagers" retrieves records with the word AIDS, but does not retrieve records which contain the word "teenagers."

The search "AIDS NOT teenagers" retrieves 301 records, only the items shown in the dark blue part of the AIDS circle.