After completing this SECTION, you will be able to:
Video Tutorial Credit: Lincoln Memorial University
What is Boolean Logic? It is the process of linking concepts in order to narrow or expand a search. Search systems will differ, but Boolean logic is a constant. It consists of three basic commands (And, Or, Not) that either expand or limit your search results.
| The AND Operator | |
| AND links two or more terms and narrows a search, retrieving only those references containing at least one term from each concept. The AND connector is very good for narrowing a search to the specific topic being researched. |
EXAMPLE: child AND abuse
![[-- Picture Example --]](http://msass.case.edu/images/harrislibrary/example1.gif) |
| The OR Operator | |
| OR links two or more terms and expands or broadens a search retrieving all records containing at least one of the search concepts entered. The OR connector is very good for linking synonyms or related concepts in order to retrieve as much relevant information as possible |
EXAMPLE: abuse OR batter OR violence
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| The NOT Operator | |
| NOT narrows a search by removing all references that contain a particular word or phrase. The NOT operator will give you fewer results. |
EXAMPLE: abuse NOT sexual
![[-- Picture Example --]](http://msass.case.edu/images/harrislibrary/example3.gif) |
Source: Case Western Reserve University
To get the best results when searching, you have to include all the variations of a word in your search. This can be frustrating as it means entering singular and plural versions, words that begin with the same stem or root, and words that can be spelt in various ways!
Then there’s the problem of keeping phrases together, so that you get an exact match rather than random instances of your keywords.
The solution? Use wildcards, truncation and phrase searching!
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Truncation/wildcard symbols assist in finding: |
Examples |
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Both singular and plural forms of a word |
Using the asterisk * truncation symbol: work* finds work, works |
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Words that begin with the same stem/root |
Using the asterisk * truncation symbol: work* finds work, works, worker, workplace etc. |
|
Words spelled in different ways |
Using the question mark ? wildcard symbol: organi?ation finds organization, organisation |
Source: University of South Australia
Phrase Searching means searching for two or more words as an exact phrase.
Unless you specify otherwise, most databases will assume the Boolean AND connector, which means that all words must be present for a particular record to be listed in the search results, but not necessarily as an exact phrase. In other words climate change should get the same results as climate and change.
Examples
In order to search for an exact phrase you must enclose the words of that phrase in quotation marks or make the appropriate choice on the database search page:
Because phrase searches are more specific than “AND” searches, they will usually retrieve fewer records. Compare the results of these two searches in OPAC:
“Climate change” finds fewer records than climate change without the quotation marks since it would not find a phrase such as change in the climate.
The Default
As you search various databases, you should determine which kind of search a particular database does unless you tell it otherwise. This is known as the default search. Some databases will default to (that is, automatically perform) a Phrase Search if you enter two or more words. Others will automatically insert an AND in between each of the words.
Help screens or search instructions for a database should tell you what the default is.
Source: Ohio University
![[-- Picture Example --]](http://msass.case.edu/images/harrislibrary/example2.gif)