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Health Sciences - Evidence Based Research Guide: Create a Search String

This guide provide information about conducting evidence-based research in the health sciences.

Creating a Search String

Research tools (library databases or internet search engines) give you the most relevant information when you convert your research question in to a search string. This is done by determining the best keywords and phrases to use in your search. A keyword describes a significant term you want to find in the resources included in your results list. A phrase is two or more keywords grouped together with quotes. Stringing several keywords together results in a search string.

When designing your search string, start with these three steps:

1.       Create a list of keywords and phrases

2.       Combine keywords and phrases using Boolean operators

3.       Use punctuation tricks

Step 1: Create a List of Keywords

The following video provides some tips for completing step 1 in the process of designing your search string. 

Step 2: Boolean Operators

Step 2 is combine keywords and phrases using Boolean operators. Boolean Operators are often used in-between keywords in a search string. 

Some search engines will search for ALL of your keywords when you enter them next to each other. For example, searching for the following: 

flu shots mandatory doctors nurses

may cause the search engine to use an implied AND to combine all terms like this for you:

flu AND shots AND mandatory AND doctors AND nurses

To better control your search you will want to design your search string with Boolean operators in the way that works best for your research question. These are words you can use to connect your keywords systematically. You can use Boolean operators to narrow or broaden your search. 

Narrow Your Search: AND is an example of a Boolean Operator: As you add more keywords, the number of documents that contain all of the keywords is going to diminish.

Expand Your Search: OR is a Boolean Operator that expands your search. In the search string example above you may not need both of the keywords doctors and nurses to be in each of the items in your results list. You can combine the doctor and nurse keywords with the OR operator to tell the search tool that either keyword is acceptable. Terms combined with OR should be set off with parentheses. Example: "flu shots" AND mandatory AND (doctors OR nurses)

Difference in the library's multi-search results for each of the search string examples.

  • flu shots mandatory doctors nurses - 313 results
  • "flu shots" AND mandatory AND (doctors OR nurses) - 566 results

Use the Boolean Operator Machine to see a visual representation of Boolean searching. 

Step 3: Use Punctuation Tricks

Step 3 is to use punctuation tricks to further refine your search. 

Parenthesis - These can used to group keywords together when using the OR operator. Example: mandated AND flu AND vaccinations AND (nurse OR doctor)

Asterisk -  Use the asterisk symbol to truncate your keywords. This means searching for all variant endings of a word. Example: nurs* will search for nurse, nurses, nursing, etc...)

Quotes - Use quotes around keyword phrases so search engines bring back results that include your keyword phrase together not separately, Example: "flu vaccinations" will bring back items that contain the phrase flu vaccinations and will not include items that have the keyword flu separate from the keyword vaccinations within the item.

Putting it all together

For the research question "Should nurses and doctors be mandated to take flu vaccinations?" a search string that includes Boolean operators and punctation tricks that will likely provide many relevant results is the following: 

"flu vaccin*" AND mandat* AND (nurses OR doctors)

Coulter Library, Onondaga Community College, Syracuse, NY