Searching for Information

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)​

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. The purple triangle in the middle of the Venn diagram to the right 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:

• 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 to the right represent the result set for this search. It is a big set because any of those words are valid using the OR operator.

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

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)

Keyword Searches

Subject Searches

Keyword or Subject Search?

• Do you know appropriate subjects?
  • Use a subject search unless you want to combine terms.
• Do you want to combine terms?
  • Use a keyword search.
• Is there little information about your topic?
  • Use a keyword search.
• Does your subject search return 'no results'?
  • Use a keyword search

Truncation:

Truncation, also called stemming, is a technique that broadens your search to include various word endings and spellings.

• To use truncation, enter the root of a word and put the truncation symbol at the end.
• The database will return results that include any word that starts with the letters in the root word, no matter how it ends.
• Examples: 
  child* will find: child, childs, children, childrens, childhood
  genetic* will find:  genetic, genetics, genetically
• Truncation symbols may vary by database; common symbols include: *, !, ?, or #

Wildcards:

Similar to truncation, wildcards substitute a symbol for one letter of a word.

• This is useful if a word is spelled in different ways, but still has the same meaning.
• Examples: 
  wom!n will find both: woman and women
  colo?r will find both: color and (the British spelling) colour