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Searching Databases: Boolean Operators

Logic Gates

In order for us to make the most out of our database searches, we need to learn how to use boolean operators.

Boolean OR

We use boolean OR when we want to select articles that have either one quality or another. Click the button below to see this operator in action.

Boolean OR

Boolean AND

We use boolean AND when we are looking for articles that have both one quality and another.

Boolean AND

Boolean NOT

Boolean NOT is used when we want articles to include one quality but completely exclude another.

Boolean NOT

Too Many Keywords

While databases can store millions of articles, it is still possible to have searches that produce no results. This is often the case when the researcher uses too many keywords on their search.

Too Many Keywords

If this happens to you, don't despair, simply go back and revise your keywords, change them, take away some, and search again.

Phrase Searching

Sometimes, when we look for articles in the databases, we look for topics like "climate change", "No Child Left Behind", "medical marijuana" or "intercontinental ballistic missile". Notice that all these topics are phrases and not single words.

In this case, it is very useful to be able to "tell" the database that we are using a specific phrase and to consider it as such. During a search, when we put quotation marks around a phrase, we are telling the database to treat the enclosed part as a phrase and to retrieve documents with the phrase in it. The example below makes this point clear.

Too Many Keywords

Too Many Keywords

Putting it All Together

How do we apply all the concepts above in our searches? Let's take a look.

Let's say we are looking for journal articles on the topic below. How do we use boolean OR, AND, NOT and phrase searching to get back the articles we need for our topic?

Using all boolean operators