Combining terms
If you have a number of key words which describe a concept - you need to use OR to search for these as you will want to find all resources which use any of these terms.
To link your concepts, use AND, as you are looking for resources which include both concepts.
Whatever source you use (even Google!) there are advantages to using the 'advanced search' option if it is available, as this will often make it easier to include your alternative terms and different concepts. Many sources offer help and guidance for searching and this can include shortcuts and tricks to improve your search.
These are called Boolean Operators.
Boolean operators
When you’ve identified your keywords, you often have to combine them to create a search strategy (or search statement). Lots of library catalogues, journal databases and Internet search engines use Boolean operators to combine keywords into search strategies.
Boolean searches are based on Boolean Logic - a system of establishing relationships between terms, devised by a 19th century mathematician named George Boole.
Boolean Logic uses only three operators or linking words : AND, OR and NOT. These help researchers to eliminate unwanted information from their search results by making the search statement a bit more precise. This is done by linking two or more search terms, using any of the Boolean operators.
Using the operators
The AND Operator
AND is used to link two search terms to narrow a search and bring back a smaller number of results. This happens because ANDing means that BOTH the search keywords MUST appear in any retrieved materials. This is represented by the area where the two circles intersect, as shown in the diagram.
The OR operator
The Boolean operator, OR, is used to link search terms to broaden a search and bring back more results. This type of search pulls back all materials containing EITHER of the search keywords. This can be useful for example, when you’re searching across British and American information sources because there are often spelling differences between the two countries.
The NOT operator
Not is used to exclude information from your search. Usually this is a subset of items within a specific category of information and is illustrated in the bottom part of the diagram.
Filters, truncation and wildcards
The purpose of filters is to narrow a search so that the number of results returned is more manageable and relevant to the researcher's interests. The types of filters available will vary according to the information source or search tool used.
Generally, the use of filters can increase the speed at which search results are returned by reducing the number of irrelevant items retrieved. But, their application is cumulative and, the application of too many filters can reduce the number of retrieved items to zero.
Truncation
Truncation involves using only the 'root' of a word to retrieve a wider variety of information than is possible using an entire word. For example, using 'search' as a search term will recover information on searching, searchers, research, researching and so on. Often you use * to search singular, plural and other versions of a term
- nurs* - to find nurse, nurses, nursing
Wildcards
Many search sources offer the possibility of using wildcard symbols (including * $ % ) in order to widen searches. So, for example, the search term wom*n would retrieve items on woman and on women.
Quotation marks: use "" to search a phrase
- "social media" - to find only the two words combined
Search support
Every source includes guidance - whether this is in a help section or elsewhere - on the filters and wildcards which can be used and how to apply them in your search.
Tips for database searching
1. Select an appropriate database depending on the search question.
2. Enter the search terms you have decided on, using advice from previous sections to combine them.
Example: for a review examining the effectiveness of an intervention, the search query may be made up of two or three sets of concepts/ terms:
- Terms relating to concept no.1 - to search for the population;
- Terms relating to concept no.2 - to search for the intervention(s);
- Terms relating to concept no.3 - to search for the outcomes (optional).
The use of more than three different search concepts is not recommended.
3. Use the subject headings from the thesaurus associated with the database.
4. Use Boolean logic AND , OR , NOT to combine search lines. (See section below or the handout for more information. )
5. Use the 'limit' options or filters provided by the database - these can include age groups, population type, date range and language. Check the help pages for the databases for more information.
6. Document your search strategy, i.e. what terms you use and how, to provide transparency for your results.
7. Consult the Help pages for each database for advice.
Tips for web searching
The internet is a valuable research tool in its own right and can offer a quick option for finding the information you need. However, as this information is less likely to have been checked for quality the way formal research usually is, it is worth taking the time to assess whether what you've found is reliable and relevant. Below are some tips on searching more effectively on Google:
- Search for a phrase: use quotation marks, e.g. “social care”. This will find results where the two words exist together.
- Exclude a particular word or phrase: put the minus sign (-) before it e.g. "mental health" -children should bring up results that exclude the word children
- Search for a particular file type: e.g. "health and social care integration" filetype:pdf should return only PDFs with your phrase in them
- Search within a website: e.g. "social care" site:knowledge.scot.nhs.uk will search for the phrase within The Knowledge Network website
- Search for related websites: e.g. related:iriss.org.uk will bring up websites related to iriss.org.uk
To make better use of Google, try using the Advanced Search by running a search from the Google homepage and then clicking on the cog at the top right of your search results. Choose 'Advanced Search' from the menu which appears.
For help to use Google Scholar more effectively, see The Knowledge Network Help pages.
For advice on how to assess the quality of information on the internet, visit our Quality Assure section.
