Boolean Searching
Boolean operators form the basis of mathematical sets and database logic.
- They connect your search words together to either narrow or broaden your set of results.
- The three basic boolean operators are: AND, OR, and NOT.
Why use Boolean operators?
- To focus a search, particularly when your topic contains multiple search terms.
- To connect various pieces of information to find exactly what you're looking for.
- Example:
second creation (title) AND wilmut AND campbell (author) AND 2000 (year)
AND / OR
Use AND in a search to:
- narrow your results
- tell the database that ALL search terms must be present in the resulting records
- example: cloning AND humand AND ethics
The purple triangle in the middle of the Venn diagram represents the result set for this search. It is a small set using AND--the combination of all three search words.
Use OR in a search to:
- connect two or more similar concepts (synonyms)
- broaden your results, telling the database that ANY of your search terms can be present in the resulting records
- example: cloning OR genetics OR reproduction
All three circles represent the result set for this search. It is a big set because any of those words are valid using the OR operator.
Search Order
Databases follow commands you type in and return results based on those commands. Be aware of the logical order in which words are connected when using Boolean operators:
- Databases usually recognize AND as the primary operator, and will connect concepts with AND together first.
- If you use a combination of AND and OR operators in a search, enclose the words to be "ORed" together in parentheses.
Examples:
- ethics AND (cloning OR reproductive techniques)
- (ethic* OR moral*) AND (bioengineering OR cloning)