Boolean Searching

Boolean searching is a logical method of connecting search terms using AND, OR, and NOT (known as "Boolean Operators") to narrow, expand, or exclude information in a search. 

Named after the mathematician, George Boole, Boolean operators (A set of terms (AND, OR, and NOT) that are used in between keywords and phrases to help create a more precise search.), are used as conjunctions that combine or exclude certain keywords in your search. Though Boolean operators are used in logic, mathematics, and computer science, there are three common Boolean operators used by search engines (e.g., library catalogs, academic databases, and some online search engines). Think of Boolean operators as instructions that tell a search engine what to do with your keywords. Some search tools need Boolean operators to be typed in all capital letters in order for them to work, so it is a good idea to always type them in all caps whenever you are using them.

AND – If the main idea contains two or more ideas, you’ll want to use AND to combine those terms in your search statement. To look for information about spiders as signs of climate change, you’ll want to have both terms in the search and perform an AND search. That’s what automatically happens in search engines such as Google and Bing unless you tell them to do something different by using OR,NOT, or-.

OR – If the main idea has several synonyms, use OR to combine them. Most search tools search for all terms (AND) by default, so you need to use the operator OR between terms to let them know you want to find any of the terms not documents with all the terms. For instance, in the previous example of Latino small business growth, we would want to also use the term Hispanic.

NOT – If the main idea has a common use you want to exclude, use NOT to exclude that word. For example, if we were looking for information about illegal drug use we would want to exclude prescription drugs from the search results. This is commonly done with NOT or the use of the minus (-) sign. In Google, to exclude a word use-word with no space between the – and the word you want to exclude. If you put a space in there, Google will not exclude the word.(When using some search tools, you have to use AND NOT before the word to exclude it.)

Images from “Search Statements” by Teaching & Learning, Ohio State University Libraries, licensed under CC BY 4.0

Emily Wixson, Boolean Operators, https://www.youtube.com/watch?v=xsSZps3NH-M

Check out this tutorial from the Leonard Lief Library at Lehman College CUNY.