If you don't put in the parentheses, the search statement is processed strictly from left to right, so that the AND is done first. This search strategy will retrieve records containing both of the concepts, Diet Therapy + Bulimia, or any records with the concept Anorexia. For example, diet therapy AND ( bulimia OR anorexia ) will retrieve records containing the two concepts, Bulimia + Diet Therapy, or the two concepts, Anorexia + Diet Therapy, or records that contain all three concepts, Bulimia + Diet Therapy + Anorexia. Searches within parentheses are performed first and operations proceed from left to right. The order in which the operations (AND, OR, NOT) are processed can vary between systems. Use parentheses ( ) to separate keywords when you are using more than one operator and three or more keywords. Nesting, or mixing the Boolean operators, is a way to combine several search statements into one comprehensive search statement. For example, you could search multi-infarct dementia by using Dementia NOT Alzheimer's.īut be careful using this because you would eliminate records discussing both types of dementia, as all articles discussing Alzheimer's are eliminated. The final Boolean operator NOT allows you to exclude concepts not relevant to your search. The more concepts or keywords you OR together, the more records you will retrieve. For example, kidney disease OR renal diseases will retrieve citations using either (or both) terms. This expands your search by retrieving citations in which either or both terms appear. The Boolean operator OR allows you to broaden a concept and include synonyms. The more concepts you AND together, the fewer records you will retrieve. For example: "Does taking aspirin cause Reye's Syndrome in children?" This will retrieve citations that discuss all three concepts in each article. Boolean search is a structured search process that allows the user to insert words or phrases such as AND, OR, NOT to limit, broaden and define the search. When terms/concepts are combined with the AND operator, retrieved records must contain all the terms. (The shading represents the outcome of the Boolean operation.) some support nesting, some databases support symbols like "&", etc.The circle diagrams that help illustrate the relationships between the sets used in Boolean logic were named after another mathematician, John Venn. Not all databases handle Boolean operators in the same way (e.g. Boolean search is based on the work of prominent British mathematician George Boole.May bring back too many, too few, or irrelevant results if keywords are not carefully selected By using the Boolean operators AND, OR, and NOT (sometimes expressed as AND NOT) between search words, a researcher can focus or broaden a search query to.Making connections between keywords or emphasizing relationships between keywords when searching.Narrowing down or broadening your search results by connecting search terms together using logic.This will narrow down your research results because the search engine will bring back only resources about the first search term (cats), but exclude any resources that include the second search term (dogs). The Boolean operator NOT tells the search engine that you want to find information about the first search term, but nothing about the second. This will broaden your search results because the search engine will bring back any results that have either search term in them. The Boolean operator OR tells the search engine that you want to find information about either search term you've entered. This will narrow down your search results because the search engine will only bring back results that include both search terms. The Boolean operator AND tells a search engine that you want to find information about two (or more) search terms. These are logic-based words that help search engines narrow down or broaden search results. Boolean searching uses operators: words like AND, OR, and NOT. Boolean searching is used to help find search results faster and with more precision.
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