Boolean Logic
Combining search statements using Boolean operators
Bolean Logic 2
Boolean searching - OR
In database searching OR expands a search by broadening the set. It is often used to combine synonyms or like concepts.
Example 1. Use Boolean logic to describe an ice cream lover with global tastes (the coloured area)
Strawberry OR chocolate OR vanilla
Bolean Logic 3
Boolean searching - AND
In database searching AND narrows a search. It is often used for linking together
different concepts.
Example 2. Use Boolean logic to describe an ice cream lover who only eats ice cream which combines 3 flavours at the same time e.g. Neopolitan ripple (the coloured area)
Strawberry AND chocolate AND vanilla
Bolean Logic 4
Boolean searching - NOT
In database searching, NOT is used to get rid of an unwanted concept.
Example 3. Use Boolean logic to describe an ice cream lover who won’t eat chocolate (the coloured area)
(Strawberry OR vanilla) NOT chocolate
But BEWARE! – you may also exclude relevant articles.
Bolean Logic 5
Boolean searching - PARENTHESES
Parentheses define the order in which the concepts are processed.
– AND takes priority– OR is processed last
HAMBURGERS EGGS
SALMONELLA
Use parentheses to ensure terms are processed as intended
Bolean Logic 6
Some examples
Example 4: Find information on the influence of eggs on salmonella food poisoning caused by hamburgers
• salmonella AND hamburgers AND eggs = food poisoning caused by both together
• (hamburgers OR eggs) AND salmonella = food poisoning caused by either
• hamburgers OR eggs AND salmonella = Do you want eggs and gastro with your hamburger, or
would you rather have fries?• (hamburgers AND salmonella) NOT eggs =
= only food poisoning caused by hamburgers (removing the confounding effect of having eggs at the same time)
Bolean Logic 7
A more complex example
Use Boolean logic to describe:
Women who have breast cancer but have never
smoked
Women who have breast cancer and who are EX-
smokers
Breast Cancer
Ex-smokersWomen
Smokers
Bolean Logic 8
Women who have breast cancer but have never
smoked
= (women AND breast cancer) NOT smokers
A more complex example
Ex-smokersWomen
Breast Cancer
Smokers
Ex-smokersWomen
Bolean Logic 9
Breast Cancer
Smokers
Ex-smokersWomen
Women who have breast cancer and who are EX-
smokers
= women AND breast cancer AND ex-smokers
A more complex example
Bolean Logic 10
Breast Cancer
Ex-smokersWomen
Smokers
Men who have breast cancer and who currently smoke
= (men AND breast cancer AND smokers)
NOT ex-smokers
Another complex example
Reference
Reference: Henderson J & Strickland J. Ithaca College Library Research Guide: Boolean Logic. Accessed at: http://www.ithacalibrary.com/sp/subjects/boolean on January 24, 2010
Bolean Logic 11