Boolean Operators: AND, OR, and NOT
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Boolean Operators: AND, OR, and NOT
Library databases, and other search engines, are often very literal. When you type words into a search box in a library database, the database searches for those words. If the resources in the database use different words to describe your topic, you may not find them. But running multiple searches on every possible keyword is time consuming and inefficient, and it doesn't give you the level of specificity you might need for your topic. Using the Boolean operators (search connectors) AND, OR, and NOT let you combine keywords into more meaningful searches. They are a core element of an efficient search strategy.
Boolean Operators Tutorial
Links to an external site.
(video by Emily Mazure, 3:02 min)
Check out the Boolean Machine Links to an external site. to visualize the effects of Boolean operators on keyword searches. (Hint: Move your cursor over each of the Boolean operators to find out how they work.)
Pretend you're writing a paper on the influence of social media on teenagers' face-to-face communication skills.
OR: When either option will do
First, you know many different ways to talk about the concept "social media." The authors of the resources you need may call it social media or social networks, or there may be a valuable resource that just talks about Facebook as an example of social media without using the words "social media" at all. Whenever you need to search for multiple options, where any of those options will do, use the search connector OR.
"social media" OR "social network" OR facebook OR twitter
Tip: The Boolean OR expands your search by returning documents in which either or both words appear. Since the OR operator is usually used for synonyms, the more words you enter, the more documents you will retrieve.
AND: When you need to find two things together
If we only search for topics related to social media, we'll find a lot of resources, but those resources could be discussing almost anything about social media: design of social networks, the use of social media as a marketing tool, etc. To make sure you're finding resources that are both about social media and communication, you'll need to search for resources where both of those concepts appear. Whenever you need to search for two concepts together, use the search connector AND.
"social media" AND communication
Tip: The Boolean AND narrows your search by retrieving only documents that contain every one of the words you enter. The more you enter, the narrower your search becomes.
NOT: When you don't want to find something
Sometimes the combination of keywords you're using will still dig up resources you don't want. For instance, in the social media example, searching for papers about the concepts "social media" and "communication" might find resources about social media's use in mass communication or marketing, neither of which is relevant to our topic of teenagers' communication skills. Whenever you need to exclude concepts from your search, use the search connector NOT.
communication NOT marketing
Tip: The Boolean NOT limits your search by returning only your first word but not the second.
Combining Connectors
All of these connectors can be combined and/or nested to help you adjust your search results. An extreme example of a search relevant to your pretend social media paper would be:
("social media" OR "social network" OR facebook OR twitter) AND communication AND (teenagers OR adolescents) NOT marketing
That looks complicated, but most library databases will have an interface that will help you divide each concept of your search into different lines, like this:
This search will find resources that contain either the words "social media" or "social network" or facebook or twitter, plus the word communication, plus either the word teenagers or adolescents, but nothing that contains the word marketing (even if it contains any of the other words).