![]() ![]() The above search will first consider the inner set of parentheses, COPD OR lung disease, finding records that contain both the search term and search phrase, or just one of them. For example: (“lung cancer” AND (COPD OR “lung disease”)) NOT asthma Likewise, nested parentheses are considered from the inside out. Just like in math, the terms or phrases contained inside of parentheses are considered together. You can control the order your search terms and phrases are searched by using parentheses to group search terms and phrases. Compound Boolean Search Syntax and the Power of Parentheses The above search will return records containing either COPD or lung disease while excluding records containing the search term asthma. For example: (COPD OR “lung disease”) NOT asthma The NOT operator can be implemented in one of two ways, either by using the boolean operator NOT or by using the minus sign ( - ) directly in front of the term or phrase to be excluded. NOT is best used when searching for a topic that often co-occurs with another topic that you wish to exclude. For more information see the Relevance section. Not all terms or phrases have to occur in the records returned, however, results are sorted by relevance, meaning records that contain a higher number of the search terms or phrases, or have a higher quality match for the fields searched, will be returned higher in the results list. ![]() The above search will return records where at least one of the search terms or phrases occurs in the records returned. For example: “lung disease" OR COPD OR “lung cancer” Use the OR operator when it is not necessary for all terms or phrases to occur in each of the resulting records. Each of the results returned will include one, several, or all of the search terms or phrases included in the query. ORĬonversely, OR is best used when you want to do a broad search about related topics. The above search requires that the records returned contain both the search term and search phrase. ANDĪND is best used to narrow search results by requiring all of the search terms or phrases in the query to occur in each record returned. It is important to understand when to use each boolean operator and how to construct compound boolean syntax to get the most out of your search. Boolean search logic is executed by using the operators AND, OR, or NOT between each search term or phrase. Use the NOT operator carefully, as it is possible to lose relevant records by accident.Boolean operators help define the logical relationship among multiple search terms and phrases. ![]() The NOT operator restricts your search, making it smaller. This search finds all records containing the word breeding, but excludes any record that includes the word genetics. You are interested in research papers about breeding but not genetics. Use this Boolean operator to exclude terms from your search. The search gets larger as you OR more terms together. This search finds records that contain one or more of the three search terms. To do this, you can use the OR operator, i.e. In this example, you want to find records that contain all the words or any of the words. This search would not find records that contain just one or two of the terms. In other words, they would be AND ed together. If you type the three terms: cattle sheep horses, CAB Direct retrieves only records that contain all three terms. You want to find research papers about cattle or sheep or horses. Use this Boolean operator to modify or refine your search. " cattle housing " and europe AND " animal welfare " OR You can type AND in either upper or lower case as shown here: The search phrase " cattle housing " europe " animal welfare " retrieves records whose indexing contains all three search terms together. ANDīy default, phrases and single words are searched in combination and are linked with the Boolean operator AND To make searching more accurate you can use Boolean operators (AND, OR, NOT) to link your search terms. ![]()
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