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Search methods & techniques: Search techniques

Search techniques - Boolean operators, phrasing, and wildcards

To use databases efficiently there are several search techniques you can use to improve the precision of your search results. These include:  Boolean operators, phrase search, and wildcards. Learn how to use these handy techniques to become more successful in your quest for information by watching the video Searching databases (4:54).

Also have a look at the module Search techniques - from snowball to cited reference search to learn more about different search methods.

Broadening and narrowing your search with Boolean operators

Despite the rather imposing name, Boolean operators are simple but extremely useful ways of either expanding or narrowing your search depending on how you use them. There are three basic Boolean operators, AND, OR and NOT, and when placed between keywords in your search they can help you to filter out unwanted results or find materials you didn’t know you were looking for. Here, we will take a brief look at each term and what they can do.




AND combines terms so that each search result contains all your terms helping you to narrow your search results. If you are looking for research on cloning sheep, use cloning AND sheep to return results that contain both keywords.




OR will look for any of your terms, so that each search result contains at least one of your terms. This will broaden your search by returning results which have either keyword. In this case cloning OR sheep gives us results about cloning but also material only focused on sheep.




NOT excludes a term from your search again helping to narrow your results but in a different way than using AND. By placing NOT before a term, any result with that keyword will not be returned. In this case, using cloning NOT sheep gives us results focusing only on cloning without any mention of sheep.



Advanced search options found in sEURch and most other search engines or databases also have built in Boolean operators as seen below from the sEURch advanced search.


Being exact with phrase searching

A phrase search is when you put quotation marks “  ” around the phrase you are searching for, and these words will then be searched next to each other in the exact order in which they were entered into the search box. So, if you look up “Migration in the Netherlands,” the search will only return results which have this exact phrase in the title, abstract, or full text. In sEURch or Google Scholar, the phrase you search for will be highlighted in bold or underlined so you can see where it appears in the text or title.



Using phrase search works for both small and large phrases. For example, a short phrase would be looking up “skin cancer,” and this will only bring up results discussing skin cancer.



However, we can expand the phrase to “skin cancer in the Netherlands” and we get a different result, one which only has articles or books discussing skin cancer in the Netherlands.



One way to use phrase searching is to speed up the process of finding an article or book that you know the title of. For example, if we want to find the article, “Only when it feels good: Specific cat vocalizations other than meowing,” all we need do is put this as a phrase with quotation marks into the search box, and, just like that, we have the article.



One problem with this type of search is that you run the risk of accidentally excluding relevant results. For example, when you search for “George Bush”, all results referring to “George W. Bush” are excluded from the results list. So, be aware of this, and that using alternative but still similar phrases might bring you more results than if you only stick with one.



Wildcards are useful for finding variant characters within a word (masking) and for finding words with different endings (truncation). This is useful when you have a keyword that could be written in different ways and you are not sure of the exact spelling, or you wish to leave it open.

Symbols used as wildcards may differ between databases. If using a database for the first time, check the search tips or help section to find out which wildcards are in use and how they work.

It should be noted that Google, Google Scholar, and Google Books do not support wildcards and truncations. Rather, Google utilizes what is called automatic stemming where if you look up the word "Run" Google will also search for "Running" and "Ran" recognizing that these are all variants of the same word. Thus, using truncation or wildcards in a Google search will hinder you rather than help you.

Wildcards in sEURch:

# replaces one character in the middle (wildcard) or at the end of a word (truncation).
There have to be at least three characters before the #

For example:
wom#n finds woman and women
recreat# finds recreate
recreat## finds recreates, recreated
recreat### finds recreation, recreating etc.

? replaces multiple characters in the middle of a word (wildcard) or at the end of a word (truncation).
There have to be at least three characters before the ?

For example:
col?r finds color, collar, collector, collier, colonizer, colour etc.
compet? finds compete, competing, competent, competence, competition, competitively, competitiveness, competitors, competitive, etc

Use ?n in combination with a number, 1-9, to specify the number of characters you want to find.

For example:
colo?1r finds color, colour
re?4tion finds recreation, refraction, relaxation, revolution etc.
compet?3 finds compete, compete?, compete! , competing, competent, etc.

* replaces all remaining characters in a word (truncation)
There have to be at least three characters before the *

For example:
compet* finds compete, competing, competent, competence, competition, competitively, competitiveness, competitors, competitive, etc


In the exercise Broaden or Narrow you can test what happens with the number of results when you use Boolean logic.