Database Search Strategies: Boolean Operators

Boolean Operators

Many databases don't understand the natural language we speak and need help understanding what we're looking to find. For this, they require a special set of conventions, including: Logical or Boolean operators, wildcard and truncation symbols, and nesting. Databases and internet search engines apply these rules differently, so check the HELP information in the database you are using to find out more.

Boolean Logic consists of three operators (connectors):

AND, OR and NOT

Boolean Operator: AND

Finds sources containing two or more ideas
The database will only retrieve items containing both words
AND narrows your search
You can use AND many times in one search
Example: electronic AND voting

Boolean AND

Boolean Operator: OR

Use OR when searching for synonyms
OR tells the database that the words can be used interchangeably, so it will retrieve items containing either word
OR broadens your search to include synonyms and related words
You can use OR many times in one search Example: electronic OR internet OR web

Boolean OR

Nesting search terms using: parenthesis ( )

Make a complex search using both AND and OR by placing parentheses around synonyms so you don't have to repeat searches
Nesting saves you time by allowing you to search multiple synonyms at once
Example: (electronic OR internet OR web) AND (vote OR voting) - this cuts down on having to do multiple searches for the combinations of keywords

Boolean Operator: NOT

Use NOT when you wish to exclude records from your search results
Example: pets NOT dogs
Be careful when using NOT! The term you want may be present in an important way in results that also contain the word you wish to avoid

Boolean NOT