Boolean searching

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 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 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.

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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