Western Libraries

Advanced Boolean Searching

Welcome to this tutorial on Boolean Operators, brought to you by the Allyn & Betty Taylor Library.

Prior to watching this tutorial, we recommended watching the video Basic Search: Using Boolean Operators.

In this tutorial we will explain why the order in which Boolean operators are used is important.

As we mentioned in the Basic tutorial on Using Boolean Operators, AND and OR are used to combine search terms to narrow and broaden the retrieval results of a search. They define the relationships between search terms, ensuring a more comprehensive search.

Is there a direct correlation between caffeine intake and breast cancer incidence rates?

We will use this research example to illustrate the importance of the order of Boolean operators.

First, we have to identify the main search terms. Here, they are Coffee and Breast Cancer. 

We will include synonyms, alternative spellings, and related terms to conduct a more comprehensive search.

In this tutorial, we will focus on the order in which the Boolean operators must be used. In the following search example, we enter Coffee OR caffeine AND breast cancer.

Our search retrieved over 25 thousands articles. This is a large number, and when looking through the article titles, many of them do not seem related to our original search.  Let’s figure out why this happened.

Usually the search system or database will perform the AND operation first.

Therefore in this example, we are searching for articles about caffeine AND breast cancer, as well as articles just about coffee.  The articles about coffee might have nothing to do with breast cancer.

To fix this problem, enter each related search term in one single box.

Type in coffee or caffeine in the 1st search box and

Breast cancer in the 2nd one.

The parentheses define the way your search is being interpreted. This way all articles about Coffee or Caffeine will be collected. Then only those articles that are also related to breast cancer will be considered and the rest will be excluded.

Our search retrieved 447 articles.   We can see from the titles of the articles that they are relevant to our research question.

When you use more than one kind of logical operator like AND and OR, you need to use parentheses to indicate what order you want things to be done in.

This is similar to mathematical equations, where the answer depends on where you place the parentheses.

1 plus 2 times 3 equals 9 or 7

Always use capital letters for Boolean operators to connect your search terms. Some databases are case sensitive and will interpret the Boolean operators differently.

Thanks for watching! Please consider viewing some of our other tutorials to learn more about conducting a literature review.