Boolean logic uses the operators AND, OR, and NOT to connect search terms when using catalogs, databases, or a web search tool.
For this research question: Does handwashing among healthcare workers reduce hospital acquired infection?
the main concepts are:
the Problem: hospital acquired infection
the Intervention: handwashing
Combine the two terms for a preliminary search.
BOOLEAN OPERATOR |
SEARCH STATEMENT | RETRIEVES | |
AND |
hospital acquired infection handwashing |
Retrieves citations with BOTH terms present |
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OR |
hospital acquired infection |
Retrieves citations with EITHER/ANY of the terms present
(OR is used to string synonyms together; remember, OR retrieves MORE!) |
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AND, OR |
(cross infection AND handwashing
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Search sets may be combined. This search locates citations with the word handwashing AND (ANY one of the terms combined with OR) | ![]() |
AND, OR |
(cross infection AND handwashing AND Publication type: randomized controlled trial |
Retrieves citations with the word handwashing AND (ANY one of the terms combined with OR) AND limited to articles with the Publication type: randomized controlled trial. (This is one example of using database Limits.) |
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NOT |
handwashing NOT masks |
Retrieves citations with the term handwashing, but omits records with the term masks (Caution: the NOT operator should be used sparingly and carefully as it may omit citations relevant to a search. For example, an article about handwashing that includes the word masks might be relevant to a search on handwashing.) |
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A SAMPLE RESULT FROM Medline/Pubmed:
Boolean logic uses the operators AND, OR, and NOT to connect search terms when using catalogs, databases, or web searching.
BOOLEAN OPERATOR |
SEARCH STATEMENT | RETRIEVES | |
AND |
driving |
AND narrows your search results to citations with BOTH terms present. |
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OR |
mobile phone |
OR broadens your results to include citations with EITHER/ANY of the terms present. OR is used to string synonyms together. Remember, OR retrieves MORE! |
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AND, OR |
driving (mobile phone |
This search locates citations with the word driving AND (ANY one of the terms combined with OR). The area where all 3 circles overlap represents search results with all criteria.
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NOT |
driving NOT cycling |
Retrieves citations with the term driving, but omits records with the term cycling (Caution: the NOT operator should be used sparingly and carefully as it may omit citations relevant to a search. For example, an article about cycling might also be relevant to driving.) |
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