Operators connecting terms

Operators connecting terms

Boolean operators form the basis database logic.

They connect your seach words together to either narrow or broaden your set of results.
The three basic Boolean operators are: AND, OR, and NOT.



Use AND in a search to:

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

Example: cloning AND animals AND ethics



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: rabbits OR hares

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:  squirrel NOT flying

It is wise to write all the Boolean operators in CAPITAL LETTERS.


Databases usually recognize AND as the primary operator, and will connect words with AND even if you don’t type it.

If you use a combination of AND and OR operators in a search, enclose the words with “OR” together in parentheses:

Example: students AND (facebook OR “social media”)

In many databases you may use the advanced search form to build up your search with drop-down menu. See more from next chapter: Basic and advanced search.

Watch a video by John M. Pfau Library (2:14) :