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Introduction to Boolean Operators

Page history last edited by Ms C. D'Alimonte 12 years, 2 months ago

Boolean Operators for Searching Subscription Databases

 

Learn how three small words can affect your retrieval when searching databases.

 

Boolean Operator #1: AND 

AND is used between words to narrow a search and retrieve fewer documents. When you use AND, you are asking the database search engine to retrieve items that include both words. 

 

Here is a sample search statement using the Boolean Operator AND

 

poverty AND crime

 

Here is a Venn diagram showing the effect of using the AND operator. The subscription database will only retrieve items that include both words you have specified, which is represented by the shaded area in the diagram.

 

 

 

Clarification: If you searched for the concept poverty by itself, you would retrieve all documents that include poverty, but if you search for povertyAND crime you will retrieve fewer documents because you are specifying that both concepts must appear.  


Boolean Operator #2: OR 

 

OR is used between words to broaden a search and retrieve more documents.

 

Here is a sample search statement using the Boolean Operator OR

 

college OR university

 

Here is a Venn diagram showing the effect of using the OR operator. The subscription database will retrieve either of the terms you have specified including both terms if they coexist in items. This is represented by the shaded area in the diagram.

 

 

 

Clarification: A search for the concept college by itself will retrieve all documents that include the word “college.” But a search for college OR university tells the database to look for occurrences of both words and retrieve documents that have either college or university or both – and this is a broader search retrieving more documents.                    


Boolean Operator #3: NOT 

NOT is used between words to exclude a term.

Here is a sample search statement using the Boolean Operator Not

 

cats NOT dogs

 

Here is a Venn diagram showing the effect of using the NOT operator. The subscription database will retrieve only items that include the specified term -- and the database search engine will not retrieve items that include the term you have decided to exclude. This means that if an item mentioned both cats and dogs, it would not be retrieved. This is represented by the shaded area in the diagram.

 

 

 

Clarification: The searcher is looking for retrieval that only mentions cats but specifically excludes anything that might mention dogs. So if an article mentioned only dogs it would be excluded and if an article mentioned both cats and dogs it would also be excluded.

 

 

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