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Introduction
to Boolean Logic
In the context of database searching, Boolean logic refers to the logical relationships among search terms.
- The Boolean operators AND, OR, NOT can be used to combine search terms in PubMed.
- In PubMed, Boolean operators must be entered in uppercase letters.
OR:
- Used to retrieve a set in which each citation contains at least one of the search terms.
- Use OR when you want to pull together articles on similar topics.
Example: football OR hockey OR soccer
Each circle in the diagram to the right represents the retrieval for each term. The grey areas represent the retrieval for this example – all records that include any one of these terms.
The table below represents sample results for each term, then for the terms combined with OR.
Search terms |
Results |
football |
4819 |
hockey |
1058 |
soccer |
2517 |
football OR hockey OR soccer |
6090 |
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Last reviewed: 28 April 2009
Last updated: 10 October 2008
First published: 20 March 2001
Metadata| Permanence level: Permanent: Dynamic Content