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Introduction to Research

Boolean Operators

Once you have identified the keywords and phrases that describe your topic, the next step is to connect them in a logical way that the database will understand - this is accomplished with the use of Boolean operators: AND, OR, NOT.

Databases and many search engines including Google make use of Boolean operators. Understanding how databases interpret your keywords will allow you to execute more specific searches, thereby saving you time while retrieving more relevant results. A database's Help pages will indicate how to construct Boolean searches and which wild cards the database supports.

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

AND - narrows a search by finding records that contain all the terms you have entered.

OR - broadens a search by finding records that contain either or all of the terms you have entered

NOT - narrows a search by finding records that contain one term but not another

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: women AND income

  • 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: < university students test anxiety > is translated to:  university 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:  "university 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: teenagers OR youth 

example of using OR between two keywords

 

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
  • use NOT sparingly, if at all, because you could end up excluding useful search results (e.g. articles or books that discuss both concepts)
  • example: exercise NOT fitness

 

Nested Searching

Whenever you have more than one Boolean operator, such as AND and OR, in a search statement, it is necessary to separate them with parentheses. This is known as a "nested searching." For example:

("fast food" OR "junk food") AND (obesity OR overweight OR fat) AND (adolescents OR teens OR youth)

Nested searching tells the database the proper order in which to search for the keywords. Operations enclosed in parentheses are performed first followed by the operators outside the parentheses.

Phrases

Use phrase searching if you want to ensure that words stay together in a particular order. Phrase searching is accomplished by placing the search terms in quotation marks.

"social media"
"junk food"

Rules about phrase searching vary from database to database.

Some databases require them (without them an AND would be assumed between each word in your phrase, or worse, the database wouldn't be able to interpret your search); others supply them for you.

The Help Screen of the database you are searching will indicate whether or not quotation marks are required.

Truncation

In many library databases (including QCAT) you can also use a truncation symbol to broaden a search.

Truncation is like a shortcut. Placed at the end of the root of a word (or word stem), a truncation symbol tells the database to search for variant endings of the word, including plurals and singulars.

Truncation symbols vary between databases. In QCAT, the truncation symbol is a question mark (?), in many other databases, the symbol is an asterisk (*).

An example of a truncated search in QCAT would be:

theat?

An example of a truncated search in an article database such as International Bibliography of Theatre and Dance would be:

theat*

QCAT and the database would interpret the search as theater, theatre, theaters, theatres, theatrical, etc.

Be careful when using truncation as it can produce unintended results. Only truncate back as far as it would be useful and still on topic.