Combining keywords: Boolean operators
Once you have selected your keywords, consideration needs to be given to how you will put your keywords together, unless you are carrying out a single keyword search. The way that you link the words can affect the way that the database retrieves information and therefore the results of the search.
Most databases use the Boolean operators AND, OR and NOT to do this. Boolean operators are now a common part of database searching. The examples of a Venn diagram below demonstrate how the database will search for information when these operators are used. You can also download the end result of the animation below.
Note that all of the Boolean operators can be used together in one query; for example, (recruitment OR employment) AND (interview OR application) NOT (Assessment AND centre).
It may be worth checking the help page of a database to see if they use these operators. Some databases require the operators to be in capitals or may use different symbols, for example & instead of AND. Boolean operators can also be used in some search engine and information gateway searches.
Boolean searching will give equal importance to each search term in a query. This means that results where a search term is discussed in a document with very little emphasis will be returned alongside those where the search term is the focus of the document (Chowdhury 2004). Some database interfaces will allow the user to account for this and search in a more effective manner i.e. by ranking the results in order of relevance. When using those databases that do not, the users will have to discern relevance for themselves.