Library and Information Science

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)

Using AND

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 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.

Using OR

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.

Using NOT

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)

Searching for multiple forms of a word

Some databases allow certain symbols to be used for searching different forms of a word (such as plurals) or different spellings. Check the help screens of a particular database to determine the appropriate symbols to use.

Plurals — a symbol added to the end of a word to instruct the database to search for plural as well as singular forms of words. The symbol used in many databases is a plus (+).

Example: drug+ retrieves drug or drugs

Truncation — a symbol added to the end of the root of a word to instruct the database to search for all forms of a word. The asterisk (*) is used in many databases for truncation.

Example: adolescen* retrieves adolescent, adolescents, or adolescence

Wildcards — a symbol used to represent any character. Wildcards can usually be used at the end of a word or within a word. The pound symbol (#) is used in many databases as a wildcard. You can use this symbol to search variant spellings of a word. You can use more than one pound sign to stand in for more than one character. Each pound sign represents 0-1 characters.

Example: wom#n retrieves woman or women
teen##### would retrieve teens and teenager and teenagers

What to look for

• Different databases interpret searches differently. A common variation is how databases recognize phrases.
• Some assume that words typed next to each other should be searched as phrases.
• Others automatically put a Boolean AND between your search terms, requiring that all the words be present, but not necessarily adjacent to each other.
• These searches can retrieve very different results.

Phrase searching tips

Most databases allow you to specify that adjacent words be searched as phrases.

• Using parentheses or quotes around search words is a common way to do phrase searching, but not all databases or search engines use them.
• Example:  "genetic engineering"
• Hint: It is often very easy to do phrase searching from the Advanced or Guided search in a database

Proximity operators

• Many databases allow you to specify that the words you are searching are within a certain proximity of each other.
• Proximity operators are more specific than Boolean operators and make your search more precise.

Proximity operator examples

Proximity operators also vary by database, but some common ones include:

w# = with

• With specifies that words appear in the order you type them in.
• Substitute the # with a number of words that may appear in between. If no number is given, then it specifies an exact phrase.
• Examples:
  genetic w engineering (searches the phrase genetic engineering)
  Hillary w2 Clinton (retrieves Hillary Clinton, Hillary Rodham Clinton, etc.)

n# = near

• Near specifies that the words may appear in any order.
• Substitute the # with a number of words that may appear in between.
• Examples:
  cloning n3 human (retrieves cloning of humans, human cloning etc.)

Citation chaining is the process by which you use one good information source, such as an article relevant to your topic, and mine its list of References for additional useful resources. This is called backward chaining. You can locate those cited articles by doing an advanced search in the Libraries' discovery layer. If you get no results in that system, try searching Google Scholar as an alternative. 

You can also do forward chaining; this identifies those who have cited the article. This is simple to do in Google Scholar. You can also personalize Google Scholar to link to articles to which the library has access.

Configuring Pratt Institute Libraries with Google Scholar

When you search Google Scholar on your personal computer, you can configure your settings so that Pratt Library resource links appear in your results. Then you can click the Find it at Pratt Link to access a library item.