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SML Research Guide: General Search Guide

A comprehensive guide for any one interested in doing a literature search in the medical/health sciences fields


The aim of this module is to provide general basic information that every one should be aware of for effective and efficient computer searching.

Basic Search Options

Searching effectively and efficiently any online resource requires understanding of the ABC of searching, this includes knowledge of below search options:

  • Boolean Operators
  • Truncation / Wildcard
  • Phrase Searching

To know what options the specific online resource you are using allows, read the "help", "search guide", "search tips" etc... before attempting to do a good search.

When more than two concepts are combined using different Boolean operators, grouping (or nesting) should be applied. This is because some computer programs process Boolean "AND" before "OR", others process "OR" before, still others process strategy from left to right, and in each processing different results are achieved (shaded part below). To override this, grouping using parenthesis should be utilized.


Grouping when applied overrides how the program processes the Boolean statement, so what is within the brackets are always processed first.  The above two examples retrieve different results as shown in the shades.

Note: some programs have a default Boolean like Google has AND as a default Boolean, so searching Google for mad cow is as if you are searching mad AND cow.

In Summary

In summary, to do a good search on any computer resource, you should read the 'help', 'search tips', 'how to search', 'search guide' and check for this particular resource what options are available and try to use them in a logical way to get more of the relevant stuff and less of the irrelevant ones.

Searching is not always error free, the success depends on:

  •    expertise of the searcher
  •    searcher’s ability to define topic precisely       
  •    how specific & accurate is the indexing 

 There is no single correct way to do every search!

Truncation / Wildcard

Truncation is a useful option that can be utilized to retrieve better results and it can be either external or internal:

External truncation allows searching for all occurrences of words that start with a specific root. OVID Medline allows external truncation by using * at the end of the word to designate zero, one, or more characters. So mutagen* retrieves mutagen or mutagens or mutagenical or mutagenic etc... This is used in keyword searching in Medline to retrieve all word variations.

Wildcard or Internal Truncation uses ? inside the word to designate a predefined number of characters usually either zero or one character.  Medline OVID allows internal truncation using ? and representing zero or one character, so colo?r retrieves either color or colour.

Phrase Search

Phrase search is used to force retrieval of two or more words next to each other, i.e. appearing as a phrase.

Search Google for mad cow, you retrieve hits that contain the two words mad and cow. This could retrieve "a mad man who had a cow", etc...

But if you are interested in mad and cow appearing next to each other, having no words in between, search the phrase "mad cow".