Why use Boolean operators?
Most library databases use Boolean operators (AND, OR, and NOT).
Use them to narrow or broaden search results.
- AND for records that include both terms (narrows search)
- OR for records that include either term (broadens search)
- NOT to exclude irrelevant concepts (narrows search)
Example:
Iran AND China AND (energy OR petroleum OR oil)
Adapted from SAIS Library, Johns Hopkins Univ. "Database Search Tips" Guide
Boolean Operators
Using AND:
- narrow results
- ALL terms must be in each search result
Note: in most, but not all, databases, the AND is implied. For example, Google automatically puts an AND in between search terms.
Example: renewable energy AND China
Using OR:
- connect similar concepts (synonyms)
- broaden results (ANY of the terms can be in the search results.)
Example: renewable energy OR solar OR wind
Using NOT:
- exclude words from search
- narrow the search
Example: peacekeeping NOT United Nations
Adapted from SAIS Library, Johns Hopkins Univ. "Database Search Tips" Guide