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Boolean searching

Boolean searching uses the words AND, OR and NOT to expand or narrow searches. They must be written in UPPER CASE so the search tool used knows not to treat them as keywords. Remember to consult any help pages to check that Boolean searching is permitted.

Using AND

Using AND in a search to combine words with different meanings tells the search tool being used to only return results that include all of the search terms. It will narrow a search and return a smaller number of results.

 

Example: a search for cloning AND genetics AND reproduction returned 5,171 results

 

In some search tools AND is implied (it is in Library Search), remember to check the help pages to see if this is the case.

Using OR

Using OR in a search to combine words with similar meanings tells the search tool being used to return results that include any of the search terms. It will expand a search and return a larger number of results.

 

Example: a search for cloning OR genetics OR reproduction returned 5,509,617 results

Using NOT

Using NOT in a search to exclude words tells the search tool being used to ignore specific words that may be implied by the keywords used. It will narrow a search and return a smaller number of results.

 

Example: a search for cloning AND genetics AND reproduction NOT sheep returned 4,880 results

 

Use NOT with caution as it could mean some useful records are excluded from your results.

Using ( ) parentheses

If OR or NOT are used in a basic search with AND, group the keywords linked by OR or NOT with parentheses (  ). This will tell the search tool being used the order the words are to be searched for. This is because many databases recognise AND as the primary operator and will connect words with AND together first which could affect the results. 

 

Example: a search for ethics AND (cloning OR reproduction) returned 16,136 results

 

Example: the same search without (  ) returned 506,556 results

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