Developing a good search strategy is essential for effective search results. Use the techniques below to help you in developing your search.
Boolean searching is based on connecting keywords with Boolean operators. The three basic operators are AND, OR and NOT. Here is how they work:
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AND Type AND between your keywords to narrow your search. The database or search engine will only retrieve those articles or web pages that contain both words. Using AND will decrease the number or hits or articles or web pages in your result list. Example: aspirin AND children
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OR Type OR between your keywords to broaden your search. The database or search engine will retrieve those articles or web pages that contain at least one of these words. Using OR will increase the number of articles or web pages in your result list. Use OR between keywords that are synonyms or have similar meanings. Example: cancer OR neoplasm |
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NOT
Type NOT before a keyword to exclude that keyword from your search. Using NOT will decrease the number of articles or web pages in your result list. The best use of NOT is when you are searching for a keyword that may have multiple meanings. Example: dementia NOT Alzheimer's
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Nesting is a concept that works hand in hand with boolean searching to combine several search statements into one comprehensive search statement. Use parentheses ( ) to separate keywords and combine like terms when you are using more than one boolean operator and three or more keywords. Searches within parentheses are performed first and operations proceed from left to right.
Let's take a closer look by examining this example from the University of Minnesota's Bio-Medical Library.
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.
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.
To search for an exact phrase, use quotation marks (" ") around the keywords.
Example: "breast cancer"
Without using (" ") the search would yield results for breast AND cancer.