Boolean logic is the process of using AND, OR, or NOT in combination with multiple keywords to manipulate how the database searches for those keywords.
Using AND narrows your search results. When placed between two keywords, the AND tells the database you only want to see articles that contain both keywords. For example, look at the following search:
This search will only show articles that reference the budget deficit in the United States. The AND ensures you find articles that match your topic as closely as possible. You can also add more keywords to be more specific:
When using the AND make sure to be specific enough to find relevant articles, but not too specific where you’re unable to find enough for your assignment.
The OR broadens search results. While the AND looks for articles that have all of the keywords, the OR tells the database to find at least one of them. Look at the following example:
The OR tells the database to find articles that mention heart attacks, as well as articles that mention myocardial infarctions. Myocardial infarction is the medical term for a heart attack, this search will find articles that use both terms.
The NOT removes articles from search results. As an example, let’s say you need research about special education in a foreign country. Run a search for special education and you’ll find that most of the articles in your search results focus on special education in the United States. However, if we conduct the following search:
This search will look for articles on special education, but will remove any that reference the United States. What is left is a series of articles focused on special education issues in countries from all over the world.
TIP: Using Boolean logic is essential to locating the best sources, but it is often a process of trial and error. If the initial search doesn't have a lot of useful sources, don’t give up! Try different combinations of keywords and Boolean logic until you find a search that works.
Limiters are additional parameters that a database can search for in addition to keywords. The limiters available depends on the database, but they can commonly be seen on the left after a search has been run, or underneath the search boxes on a database's home page. Here is an example of what they look like:
Check the box for 'Limit to Full Text' to remove articles that don't have immediate full-text access. 'Limit to Peer Reviewed' filters out articles not published in a peer reviewed journal. Another useful limiter allows for the specification of an article's publication date. Specifying a date range removes any article published outside of that time frame.
When looking at the results of a search, Subject Headings are a great way to evaluate article. In most databases, under the title of each article should be information such as author names, journal title, volume and issue information, and other key pieces of information. After that, very often there is a list of keywords. These are the Subject Headings:
Subject headings list the major topics an article covers. Reading subject headings provides an idea of what can be expected in the full text. They are a great way of skimming search results to identify articles worth investigating more thoroughly.
Field Searching specifies where a database will search for keywords in order to narrow and make search results more specific. Here is an example of an Advanced Search in a database:
To the right of the empty search boxes are drop-down boxes. The default selection is 'Select a Field (optional)'. When left alone, the database searches for keywords in a few pre-determined places (the article title, subject headings, and abstract to name a few). If keywords are found in those areas it is likely an article will be relevant.
The drop-down boxes provide the option to search for keywords in specific locations. In the above example, the drop-down box to the right of 'capitalism' is set to 'TI Title'. The database will search for articles where 'capitalism' is in the title, ignoring any that do not.
Truncation is one of the most valuable research tools to use in database research. Here is an example of truncation:
The first search box has 'manag*' in it. There are two things to note here. One, “manage” is not completely spelled out. Two, an asterisk is at the end of the keyword. In this context, the asterisk is known as a wildcard. Cutting off the end of the keyword and adding a wildcard is truncation.
The wildcard takes what is typed in front of it (in this case manag*) and searches for every complete word it can create with it. In this case search results will contain: manage, manages, manager, managers, management, managed, managing. Very often, different variations of a root word are all useful. Truncation allows for the searching of all these variants without typing them out individually.
When using truncation, consider if the keyword has any different endings. If so, are any of them potentially useful? Be sure to cut off the word at the point where all of the variants stop being the same. Add the wildcard at that point.