Databases Search Techniques

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Database Search Techniques

There are various ways to build a search strategy.  Click on the links below to move to the relevant section.

Boolean Operators

To combine concepts (and their synonyms) we use AND and OR, referred to as Boolean operators.


Boolean AND example image

To find articles which contain all of your concepts:

  • Combine them with AND
  • Using AND narrows your search. The more words you combine with AND,the smaller your search results will be.
  • Examples:
    allergens AND asthma AND children


Boolean OR example imageTo find articles which contain any of your keywords:

  • Combine them with OR
  • Using OR expands your search. The more words you combine with OR, the larger your search results will be.
  • Examples:
    (acute OR chronic OR bronchial) AND asthma


To eliminate non-relevant results:

  • Combine with NOT
  • Using NOT reduces the number of results you find.  Use with caution as you may inadvertently remove results of interest
  • Examples:

      (enzyme NOT signalling) AND nanoparticle


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

  • both the singular and plural forms of a word
  • words that begin with the same word stem
  • Truncation symbols vary by database; common symbols include: *, ?, #, $
  • Examples:
    child* = child, childs, children, childrens, childhood
    genetic* = genetic, genetics, genetically


Wildcards broaden your search to include words with different spellings.

  • This is useful if a word is spelled in different ways, but still has the same meaning.
  • Wildcard symbols vary by database; common symbols include: #, ?
  • Examples:
    wom#n = woman, women
    colo?r = color, colour

Proximity Operators

Proximity operators allow you to indicate how closely two search terms are positioned to each other. Words that are close to each other are more likely to be relevant than words that are widely separated.

  • Using proximity operators will limit your search, resulting in a smaller search result.
  • A proximity operator has two components:
    • letters which indicate a specific search syntax
    • a number that indicates how close the words must be to each other
  • Proximity operators vary by database; common symbols include: N5, W3, NEAR/4, adj2
  • Examples:
    allergies N5 asthma  (to find the words allergies and asthma within 5 words of each other)
    allergies NEAR/5 asthma 

Phrase Searching

To find an exact phrase use quotation marks.

  • Examples:
    "chronic disease"
Content last updated: December 4, 2019