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Database Searching Tips

Why use Boolean operators?

The three basic Boolean operators are AND, OR, and NOT.  Using them properly can help:

  • connect your search words together to either narrow or broaden your set of results
  • focus a search, particularly when your topic contains multiple search terms

  • connect various pieces of information to find exactly what you're looking for


Iran AND China AND (energy OR petroleum OR oil) 

Using AND

Use AND in a search to:

  • narrow your results
  • tell the database that ALL search terms must be present in the resulting records

Note that in many, but not all, databases, the AND is implied. For example, Google automatically puts an AND in between your search terms.

Example:  renewable energy AND China

AND Boolean Operator example: Renewable energy AND China

Using OR

Use OR in a search to:

  • connect two or more similar concepts (synonyms)
  • broaden your results, telling the database that ANY of your search terms can be present in the resulting records

Example:  renewable energy OR solar OR wind


OR Boolean Operator example: renewable energy OR wind OR solar

Using NOT

Use NOT in a search to:

  • exclude words from your search
  • narrow your search, telling the database to ignore concepts that may be implied by your search terms

Example:  peacekeeping NOT United Nations

NOT Boolean Operator example: peackeeping NOT United Nations

Search order

Databases return results based on the commands (searches) you enter. Be aware of the logical order in which words are connected when using Boolean operators: 

  • Databases usually recognize AND as the primary operator, and will connect concepts with AND together first.
  • If you use a combination of AND and OR operators in a search, enclose the words to be "ORed" together in parentheses.


democratization AND (Thailand OR Malaysia)