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Boolean Logic

Boolean operators allow you to search for combinations of words or phrases. Operators are used to broaden or narrow the search by combining words or phrases. Boolean searching can be used when searching the internet or online catalogs and databases; however, it is important to take notice of specific database requirements since many have their own Boolean template.

Boolean logic allows you to broaden or narrow your search by combing words or phrases using the Boolean operators AND, OR, and NOT.

The results of performing Boolean searches are illustrated by the diagrams below (called Venn diagrams). The diagrams show graphically how using the AND operator narrows a search, using OR broadens a search and using NOT excludes material from a search.

Operator Example Search The search will find... Venn diagram
AND women AND marketing items containing "women" and "marketing." AND narrows a search, resulting in fewer hits.
  • Use AND to combine two ideas when both are important to our search

OR global warming OR greenhouse effect items containing either "global warming" or "greenhouse effect" or both. OR broadens a search, resulting in more hits.
  • Use to include synonyms or alternate terms in your search.

NOT Caribbean NOT Cuba items containing "Mexico" but NOT "New Mexico." Caution! It's easy to exclude relevant items.
  • Excludes records containing the second term.

For additional assistance contact Lydia Jackson, Instruction Librarian ( ljackso@siue.edu or 618-650-2604) or the Information Desk (618-650-INFO).

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