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Database Searching: Using Boolean to Empower Your Search: Boolean Logic

What it is and how it can help you turn your keyword terms into power searching!


George Boolean

George Boole


Inventor of Boolean Logic

George Boole was a 19th century mathematician and philosopher (1815-1864).  He invented what we refer to as Boolean logic, a method of combining factors to limit or increase results.  Boolean logic utilizes the operators AND, OR, and NOT to describe what will or will not be included in search results.

e.g. Strawberry OR Vanilla OR Chocolate


Strawberry AND Vanilla AND Chocolate


Strawberry OR Vanilla NOT Chocolate 

How Boolean Works: OR, AND, NOT


Using synonyms
Increasing recall

When you are searching for a concept that may be described using several synonymous terms (e.g. car, automobile, vehicle) you want to increase your recall by linking these synonyms using OR.  When you search for car OR automobile OR vehicle the search engine will retrieve results that include at least one of these terms.

Takeaway point: The OR term brings back anything and everything.  It is best used for searching for synonyms (cats OR felines) in order to increase recall.


Multiple concepts or ideas
Refining results

If you were looking for something very specific, say an article or book that includes all of the terms car, automobile, and vehicle, you would want to increase relevance by using the AND operator.  Doing this will bring you only results that include all three terms.

Takeaway: The AND term is limits your search, and is best used for combining different concepts (presidents AND statues) and for refining results (cats AND breeds).


Distinguish between multiple meanings
Eliminate specific sub-topics
Fine-tune broad topics

If you want to be the most specific and you are looking for results that include one particular term and don't include variations, you can use the NOT operator.  So if you are looking for results that include only the term car but not the terms automobile or vehicle you would search for car NOT automobile NOT vehicle.  This will exclude any items that include those two terms from your results.

Takeaway: The NOT operator is best used to exclude confounding terms or concepts (e.g. nursing NOT motherhood), eliminate specific subtopics (horsemanship NOT bridling), or fine-tune broad topics (cats NOT wild).

Boolean Demonstration

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