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Boolean Operators

Choosing Keywords | Boolean Operators | Phrase Searching & Truncation

Now that you have identified your keywords (or search terms), it is time to combine them with Boolean operators to create a search string. 

AND, OR, NOT

In Boolean searching, these three words (or operators) act as commands: AND, OR, and NOT. Combining keywords with a Boolean operator creates a search string tells the computer to narrow or broaden your search results.  

To learn more, watch this Searching Effectively: Boolean Operators tutorial, and then read the information below.  


 

Comparing Boolean Operators

The results of performing Boolean searches are sometimes illustrated by Venn diagrams. The diagrams illustrate how using the AND operator narrows a search, using the OR operator broadens a search, and using the NOT operator excludes material from a search. The green section in each diagram represents the results for each search.

OperatorSearch String The search will find...Venn Diagram Results
AND oregon AND volcano sources that mention both oregon and volcano.
AND narrows a search, resulting in fewer hits.
OR butterfly OR moth sources containing either butterfly or moth or both.
OR broadens a search, resulting in more hits.

NOT
cowboys NOT dallas
items containing cowboys but not dallas.
NOT narrows a search, resulting in fewer hits.
Caution! It's easy to exclude relevant items.


Examples of Boolean Search Strings in an Online Catalog, a Database, and a Search Engine

 

    • Online catalog example, using the AND operator, in an advanced or Power search screen



    • Search engine example, using the OR operator, in basic search box

    • Database example, using the NOT operator, in an advanced search screen


 

Next => Once you have combined keywords with Boolean operators, it is time to learn two more search strategies -- phrase searching and truncation

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