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Advanced Search Techniques Boolean Operators

Learn about advanced search strategies for databases and search engines.

About Boolean Operators

Boolean operators use AND, OR, NOT to limit or expand a search. (Note the capitalization. Many databases require operators to be in all caps, as do search engines like Google, which also allows for Boolean based searches.)

  • AND narrows a search by requiring the results contain both of the search terms connected by AND.

In other words, the search results will contain search term X and search term Y.

  • OR broadens a search and is usually used when searching related or similar terms.

In other words, the search results will contain search term X or search term Y or both.

  • NOT narrows searches by excluding sources with a specified search term.

In other words, the results will not contain search term X.

Boolean operator searches can be simple, e.g., Moose AND Elk; Moose NOT Elk. Or they can be more complex and nuanced when combining operators and use parentheses, e.g., (Caribou AND Elk) NOT Moose; (Moose OR Elk) NOT Caribou.

Boolean Operator: AND Example

Boolean operator AND usage is demonstrated by two connecting circles. A search for unemployed AND underemployed will return only results that mention both terms. This is demonstrated by the area where the two circles overlap and is highlighted in green.

Example Search

Using the Boolean Connector, AND, will return more relevant search results. It will exclude results that only mention one or the other, and return results that mention both. The example searches for both search terms, unemployed AND underemployed.

A search conducted in the ABI/INFORM collection database using the search string: (unemployed AND underemployed)

Boolean Operator: OR Example

Boolean operator OR usage is demonstrated by two connecting circles. A search for “cell phone” OR “mobile phone” will return results that mention both terms or just one term.. This is demonstrated by both circles as well as the overlapping area being highlighted in green.

Example Search

Using the Boolean Connector, OR will return more search results. The example searches for both search terms, "cell phone" OR "mobile phone."

A search conducted in the ABI/INFORM collection database using the search string: (“cell phone” OR “mobile phone”)

Boolean Operator: NOT Example

Boolean operator NOT usage is demonstrated by two connecting circles. A search for unemployed NOT retired will return only results that mention unemployed without retired. This is demonstrated by the area where the two circles overlap being grayed out as well as the circle containing retired. Only unemployed is highlighted in green.

Example Search

Using the Boolean Connector, NOT will return fewer search results. The example searches for the search term unemployed NOT retired. This will exclude results that discuss retired when searching for unemployed.

A search conducted in the ABI/INFORM collection database using the search string: (unemployed NOT retired)