Combining Search Terms- Boolean Operators

The final step of developing an effective search strategy is combining the search terms and keywords/key concepts you have identified using Boolean Operators.

Boolean Operators

Definition:  The three Boolean Operators are OR, AND, and NOT.  When doing research the operators are used to connect words or phrases to either limit or expand a search.

AND

A Boolean Operator used to limit your search by ensuring that all keywords used appear in the search results.

EXAMPLE:  I'm interested in knowing if there is a relationship between stress and sleep walking.

stress AND sleep walking

In this search we retrieve records in which Both of the search terms are present.

This is an example of how AND logic works in searching a database.

The more terms or concepts we combine using AND logic, the fewer records we will retrieve.

dyssomnias AND parasomnias AND insomnia

Here is an example of how using multiple search terms with AND will effect your database searching.

OR

A Boolean Operator used to expand your search by retrieving any, some or all of the keywords used in a search statement.

When you put together concepts with OR, you are requesting documents containing at least one of the terms.  OR is used to join synonyms or related terms and is considered an expander because it broadens the search and increases the number of documents you would have retrieved if you had only used one term.

Example:  I would like information about somnabulism.
Somnambulism is a synonym for sleep walking.

somnambulism OR sleep walking

In this search, we retrieve records in which AT LEAST ONE of the search terms is present.  We are searching documents that contain either of the terms somnambulism or sleep walking.

OR logic is most commonly used to search for synonymous terms or concepts.

This is an example of how OR logic works in a database search.

NOT

A Boolean Operator used to eliminate an unwanted concept or word in your search statement.

Example:  I want to learn about parasomnias, but I want to eliminate information on night terrors.

parasomnias NOT night terrors

In this search, we retrieve records in which ONLY ONE of the search terms is present.

Here is an example of how NOT logic works in a database search.

BE CAREFUL

NOT logic excludes records from your search results.  It's easy to exclude relevant items!

"Now that you have completed, Combining Search Terms-Boolean Operators, let's move onto the next section.  To proceed, click on the Selecting a Database link below."

What is a Research Strategy? | Selecting a Topic & Locating Background Information | Formulating a Search Statement | Identifying Keywords/Key Concepts | Subject Searching | Combining Search Terms -- Boolean Operators | Selecting a Database | Documenting Your Research | Analyzing Information Sources | Evaluating Results | Glossary