Boolean operators form the basis of 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)
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 humans AND ethics
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The purple triangle in the middle of the Venn diagram below represents the result set for this search. It is a small set using AND, the combination of all three search words.
Be aware: In many, but not all, databases, the AND is implied.
- For example, Google automatically puts an AND in between your search terms.
- Though all your search terms are included in the results, they may not be connected together in the way you want.
- For example, this search: college students test anxiety is translated to: college AND students AND test AND anxiety. The words may appear individually throughout the resulting records.
- You can search using phrases to make your results more specific.
- For example: "college students" AND "test anxiety". This way, the phrases show up in the results as you expect them to be.
Use OR in a search to:
Use NOT in a search to:
- exclude words from your search
- narrow your search, telling the database to ignore concepts that may be implied by your search terms
- example: cloning NOT sheep
Credit: MIT Libraries: Database Search Tips: Boolean Operators.
