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COLL S103 The Critical Issue Philosophy Film and Music

Why use Boolean operators?

Most library databases use Boolean operators (ANDOR, 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 (no longer extant).

Boolean Operators

Use AND, OR, and NOT to narrow or broaden search results.

Using AND

  • narrows 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

  • broadens results
  • searches for ANY of the terms in search results
  • connect similar concepts (synonyms)


Example:  renewable energy OR solar OR wind


Using NOT

  • narrows results
  • exclude words from search

Example:  peacekeeping NOT United Nations


Adapted from SAIS Library, Johns Hopkins Univ. "Database Search Tips" Guide (no longer extant).

Too Few Results?

Don't give up! Reassess your search strategy.

Possible Reasons:

1. Choice of Search terms
Choosing the right search terms is key.

  • Experiment with related terms.
  • In databases Subject Terms can help you identify keywords.
  • Use OR to search for multiple related terms simultaneously. (e.g., policy OR law)

2. Too Many Search Terms
Database can be picky about search terms. Be selective.

  • Begin with one of two search terms that best represent your topic. Then add other terms as needed.
  • Avoid long phrases and empty words like “the” and “how.”

3. Too Many Limiters
If you limited the search (e.g., by date or search field) remove limiters and reassess.

4. Narrow Topic
Highly specific topics may be too narrow for finding results. Try a broader related topic first. 


  • Narrow search: Bloomington Indiana AND environmental policy
  • Broader search: United States AND state government AND environmental policy

5. Database Choice
Different databases focus on different topics. View Resources by Subject or Ask a Librarian.

Too Many Results?

1. Add additional keywords.

  • TIP: In databases Subject Terms can help you identify more narrow topics and keywords.

2. Choose more narrow search terms.


  • Broader term: law
  • Narrower term: "environmental law"

3. Use limiters. (e.g., search fields like title or abstract, publication date, format type).

   In OneSearch see options under Refine Search.

4. Search for a short phrase with quotation marks. 


  • "environmental law"
  • "environmental justice"