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ENGL 100 Webster (Spring 2022)

Advanced Search Techniques

If you're having trouble searching for information, and you're getting too many results, not enough results, or maybe the results you're getting just aren't quite right, try some of these advanced search techniques. Much of the information on this page comes from MIT Libraries' Database Search Tips research guide.

Boolean Operators

Boolean operators connect your search words together to either narrow or broaden your set of results.

The three basic Boolean operators are: ANDOR, and NOT.

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

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

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.


  • ethics AND (cloning OR reproductive techniques)
  • (ethic* OR moral*) AND (bioengineering OR cloning)

Truncation (library databases only)

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.
  • Truncation symbols may vary by database; it's most commonly *, but can also include: !, ?, or #. Check the individual database help pages or advanced search to be sure.
  • Examples:
    child* = child, childs, children, childrens, childhood
    genetic* = genetic, genetics, genetically

If I was searching for something related to libraries I could either search using the Boolean operator OR, or I can search by truncating at the root. For example: (library OR libraries OR librarian OR librarians OR librarianship) searches can be truncated to librar*.

Things to look for:

  • Root words that have multiple endings. Example: sun = suns, sunshine, sunny, sunlight
  • Words that are spelled differently, but mean the same thing. Example: color, colour

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.
  • You can click a button specifying that you want your words searched as a phrase.

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.

What are subject headings and keywords?

Subject headings describe the content of each item in a database. Use these headings to find relevant items on the same topic.  Searching by subject headings (a.k.a. descriptors) is the most precise way to search article databases. In most library catalogs, Library of Congress Subject Headings (LCSH) are used. In research databases the database vendor maintains their own thesaurus. 

It is not easy to guess which subject headings are used in a given database. You often have to perform a keyword search to discover the subject heading used by the database.

Keyword searching is how you typically search web search engines.  Think of important words or phrases and type them in to get results.

Her are some key points about each type of search.

  • natural language words describing your topic - good to start with
  • pre-defined "controlled vocabulary" words used to describe the content of each item (book, journal article) in a database
  • more flexible to search by - can combine together in many ways
  • less flexible to search by - need to know the exact controlled vocabulary term
  • database looks for keywords anywhere in the record - not necessarily connected together
  • database looks for subjects only in the subject heading or descriptor field, where the most relevant words appear
  • may yield too many or too few results
  • if too many results - also uses subheadings to focus on one aspect of the broader subject
  • may yield many irrelevant results
  • results usually very relevant to the topic

When you search a database and do not get the results you expect, Ask a CSM Librarian for advice.

Things to look for:

To find subject headings for your topic:

  • Look to see if the database has an online thesaurus to browse for subjects that match your topic (check the Help screens).
  • Some databases publish thesauri in print (e.g. Thesaurus of Psychological Index Terms for the PsycInfo database). Ask a CSM Librarian for help using thesauri.

Another way to find subject headings:

  • Start with a keyword search, using words/phrases that describe your topic.
  • Browse the results; choose 2 or 3 that are relevant.
  • Look at the Subject or Descriptor field and note the terms used (write them down).
  • Redo your search using those terms.
  • Your results will be more precise than your initial keyword search.

Advanced Search Operators

These generally work in both search engines and research databases. When in doubt, look for and click on Advanced Search.



cats dogs

Results about cats and dogs

(both words will appear in results)

cats OR dogs

Results about cats or dogs

(either word will appear in results)

cats -dogs

No dogs in results (search engines)

cats NOT dogs

No dogs in results (some library databases)

"cats love dogs"

Results for the exact phrase cats love dogs

dogs AND (rats OR snakes)

Results about dogs and rats or dogs and snakes,but not rats and snakes.


Advanced Search Operators (search engines only)



cats filetype:pdf

PDFs about cats. Supported file types include: pdf, doc(x), xls(x), ppt(x)


Pages about dogs from


Pages about cats excluding


Page title includes the word dogs


Page URL includes the word cats