Boolean logic was named after the 19th century mathematician George Boole, who created a form of algebra in which all values can be reduced to either TRUE or FALSE.
The three basic BOOLEAN operators are OR, AND, and NOT, which we will discuss in later slides
Each search engine and database uses Boolean operators in a slightly different way or may require the operator to be typed in all capitals or have special punctuation.
For example: A search for dog or canine can result in documents containing the word dog (but not canine) and other documents containing the word canine (but not dog) as well as documents with both dog and canine mentioned in either order or number of uses.
Using Boolean Operators in Your Search
Why Use Boolean Logic?
Why use Boolean logic?
• Connects your search terms together to
either narrow or broaden your results
• Helps you piece together information to find
exactly what you’re looking for
• Yields more accurate results
1815 - 1864
Using Boolean Operators
• Common words are used as logical operators
AND = results meet both or all of the criteria
OR = results meet at least one of the stated criteria
NOT = results do not contain the specified terms
• Boolean operators vary
Be sure to check the database’s “Help” information or “Search Tips” for
details about which term/symbol to use
Boolean Search Operator: AND
• Narrows your search
• Retrieve less results
• Results will include both (or all) keywords
• Connects unrelated concepts
Example: “global warming” AND “sea level”
butterfly AND migration
Boolean Search Operator: OR
• Broadens your search
• Retrieve more results
• Results will include one, or the other, or all terms
• Used to connect synonyms and related concepts
Examples: kids OR children OR youth
dog OR canine
Boolean Search Operator: NOT
• Narrows your search
• Excludes items by ignoring results that use
the specified keyword(s)
• Use sparingly! You may filter out relevant
results by excluding certain keywords.
Example: Alzheimer’s NOT dementia
Boolean Search Modifier: Quotation Marks “”
• Use quotation marks to search for an EXACT phrase
• Keeps 2 or more words together
Example: “death penalty”
Without quotation marks, the database would separately search for
death AND penalty, not necessarily those words together.
Boolean Search Modifier: Asterisk*
• Truncation: Shortening a word to pick up variants
A form of the Boolean operator, OR
Also called “stemming”
• Common truncation symbol: * [asterisk]
• Symbol should be placed at the end of the word root
hum*- Avoid placing the truncation symbol too soon
If you were searching for variants of humor, your search will retrieve unrelated terms like humble,
hummus, human, etc.
→ pollution, pollutant, polluted, pollute, polluting, polluter
→ adoption, adopter, adopting, adopts
→ alcohols, alcoholic, alcoholism
Boolean Search Modifier: Parentheses ( )
• Nesting: Group keywords together using parentheses to make a complex
• Search multiple synonyms (words connected by OR) at once
• Do not use parentheses to combine keywords connected by AND
Example: (children OR adolescents OR youth) AND depression
(Hanukkah OR Chanukah OR Hanukah) AND tradition
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