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Searching Solutions: Boolean Searching

Understanding how searching changes from search engine to database.

Boolean Concepts

Boolean searching (named after George Boole) is used by most databases to focus searches. Examples of each term and search strategy are given below. A few tips to start:

  • Three Boolean operators are recognized by most databases: AND, OR, and NOT
  • The operators must be written in ALL CAPS (there may be exceptions, but this is good practice and helps you keep track of your search terms)
  • The default in most databases is to combine the terms with the AND operator ("Ilene health 2015" becomes "Ilene AND health AND 2015")
  • Use a NOT operator to exclude terms from your search (see Example 3 below)
  • Databases generally have an order in which they process Boolean terms, but that order may differ between databases; Use parentheses to change the processing order
  • Always check the parentheses after a search to be certain the database put them where you expected
              osteoporosis AND ("Alzheimer’s disease OR "Parkinson’s disease")
    is not the same as
              (osteoporosis AND "Alzheimer’s disease") OR "Parkinson’s disease"
    (see below, 4. Examples, for additional examples)
  • Use quotation marks for phrases (unless you are using a database with automatic term mapping - like PubMed)


Use AND to connect two or more concepts

  • Narrows your search
  • Retrieve less results
  • Results will contain both concepts

Example 1:
classroom management AND student behavior


Some databases use "+" instead of (or in addition to) AND.

Other search options

In addition to Boolean terms, search strategies can include other options including Proximity Indicators (e.g., NEAR, ADJ, and PRE), truncation or Wildcard symbols (?, and *), the hyphen (-), and specialized options (e.g. SAME or EXACT). See the Additional Search Options tab.


Use OR to connect two or more similar concepts (synonyms)

  • Broadens your search
  • Retrieve more results
  • Not all results will contain both concepts

Example 2:
assessments OR evaluations

4. Examples

Here are a number of examples in combining three concepts with Boolean terms.

  • engineer AND Latino AND arthritis = 7 (only articles that include all three concepts)
  • engineer OR Latino OR arthritis = 1+2+3+4+5+6+7 (any article that contains any of these concepts)
  • engineer AND Latino = 5+7
  • (engineer AND Latino) NOT arthritis = 5
  • Latino OR engineer = 1+5+2+4+6+7
  • (engineer OR Latino) NOT arthritis = 1+5+2
  • engineer OR (Latino NOT arthritis) = 1+5+2+4
  • Latino NOT arthritis = 5+2

Boolean Example


Use NOT to exclude concepts from your search.

  • Narrows your search
  • Tells the database to ignore results with one concept - even if those results contain other concepts used the search

Example 3:
osteoporosis NOT arthritis

Boolean NOT

Some databases use "-"  or AND NOT instead of NOT.

Additional Resources