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EPI 0950 -Field Experience Professor E. Costello: Boolean Operators

This guide is for the course EPI 0950 -Field Experience


When using the Library's databases you need to develop a common search techniques that can be applied to any database. This includes coming up with your keywords, using the right Boolean operator to combine your keywords, and knowing which fields to search. This is important since searching the Library's databases is not the same as searching Google.

Boolean operators

What are Boolean operators:

Boolean operators are derived from mathematical sets and database logic. They connect your keywords to tell the database to either narrow or broaden your results so that they are specific and relevant to what you are searching for.

The three main boolean operators are: ANDOR, and NOT.

AND is used to narrow your results as it tells the database to include all of your search terms in the results

  • example: communication AND relationship AND community

The section the middle of the Venn diagram below represents the result set for this search. Your results will be fewer using AND, since they will contain alll three search words.

Be aware that some databases like Google automatically inserts AND between your keywords but even though all your keywords are included in the results, they may not be connected in the way you would like.


OR is used in a search to connect two or more similar concepts (synonyms) and to broaden your results, telling the database that ANY of your search terms can be present in the resulting records

  • example: safety OR wellbeing OR protection

All three circles represent the results for this search. The results may be many as the databases will include any of your keywords words.


NOT is used to narrow your search results by excluding keywords exclude

  • example:  safety NOT wellbeing