Searching Databases: Boolean Basics

 

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Home >> Research Services >> Research Services Blog >> Searching Databases: Boolean Basics
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Struggling to find articles in a library database?

Read on to find out how the words AND, OR, NOT, can help you research more effectively.

Databases have a huge amount of information within them. To more effectively mine through this data, use the search syntax or searching rules to improve your search results.  This means you need to use the Boolean operators of: AND, OR, NOT to create search strings using your keywords.

  • AND
    • Tells the database to return results that include both the keywords.  Links different aspects of your research question together to find both concepts in the set of returned results.
    • Narrows your results.
  • OR
    • Tells the database to return results that include either of the keywords.
    • Links synonymous terms or concepts.
    • Expands your results.
  • NOT
    • Tells the database to return results that do not include a certain keyword.
    • Rids results of items that that contain a certain element of research topic.
    • Narrows your results.

Advanced Search Techniques:

  • Using Quotations
    • Requires keywords to be searched as a phrase.
    •  Finds “Global warming” instead of the default AND between keywords: Global AND warming
  • Using Parentheses
    • Parentheses allow you to create more complex search strings.
    • Think of Boolean like a math problem.  The database will process some of the Boolean operators before others unless there are parentheses.  Order of precedence of Boolean operators is: AND, NOT, OR. That is, an AND operation will be performed before an OR operation if both operations are included in a query, unless parentheses are used to override priority of search operators. Expressions in parentheses are processed first.
    • Especially useful when using OR operator in between similar concepts.
    • Ex. (ethics or morality) and cloning- Searches for articles with either ethics or morality AND the keyword cloning.
  • Using Truncation
    • Truncation, also called stemming, is a technique that broadens your search to include various word endings and spellings.
    • To use truncation, enter the root of a word and put the truncation symbol at the end.
    • Truncation symbols may vary by database; common symbols include: *, !, ?, or #
    • Examples:
      child* = child, childs, children, children’s, childhood
      genetic* = genetic, genetics, genetically

Next Steps:

Another piece of the puzzle is finding the correct database to perform these searches.  Check out the research guide in the subject area you are working within to get a list of preferred databases for that topic. These are listed under the Article tab.  The Research Services Desk and subject specialty Librarians are also great resources to ask if you get stuck trying to decide which database to search in on your topic.  Now that you understand the basics of formulating a search strategy, you should find that you search results are much improved.

Want more information on Boolean? Check out the following links:

Written by: Brittany Geissinger Questions? Brittany.Geissinger@mail.sdsu.edu

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"Global warming" or "greenhouse effect" venn diagram
Mexico not "New Mexico" venn diagram

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