Help with Boolean

The most commonly used operators are AND and OR.    AND is used to narrow a search.  For example, if I am researching the topic of the effect of global warning on the polar ice caps, then I want articles that contain both of those terms.  As a result, my search would look like this: global warming AND ice caps.    If I searched global warming OR ice caps, then I would find articles that contained either one of those terms - but not necessarily both.  To explain further, the results might contain just the term global warming or just the term ice caps (and thus not be what I'm looking for, because I want both of the terms).  This is why AND narrows a search - I'm telling the database or search engine that ALL of the terms must be present in the results.

OR is used to broaden a search. Typically, you want any terms linked with OR to be like terms or synonyms - for example, global warming OR climate change.  OR then broadens the search by providing alternative, related terms to search. When you link terms with OR, put them in parenthesis (global warming OR climate change) - this helps the database put the search in the right order (without nesting, your results may not be what you expect, because the search engine needs them to interpret your search. Nesting should not be used with single terms or phrases - that's where you can employ quotation marks (explained a bit later).  NOT can also be effective if you want to eliminate a certain term...but it is not used as often as AND & OR.  One way that I use NOT is when I want literary criticism about a book or author, but not a book review of that author's work.  So I might say "Nathaniel Hawthorne" AND "Scarlet Letter" NOT "book review" to weed out the book reviews from my results.

Some other techniques to use are quotation marks - so, if I searched "global warming," I'm asking to find those two words right next to each other.  If i search without the quotation marks, then the word global might appear in one paragraph, and the term warming in another.  So, putting short, common phrases ("instant messaging," "global warming") in quotation marks simply increases your chances of retrieving highly relevant results.

Truncation can also be effective, but you have to be careful that you're not truncating so far back that you end up retrieving many unrelated terms.  You also don't need to use the truncation symbol (*) if you all you would retrieve is the plural of the word - databases will usually automatically retrieve the plural (for example, there's no need to do this: daughter* - the database will retrieve both daughter and daughters without the symbol)   So, a more detailed search statement might look like this: ("global warming" OR "climate change") AND "ice caps".  What you want to avoid is searching in long phrases, or using phrases that contain words like of, from, etc.  You want to pick out the key terms/concepts in your research question, and then link those terms with Boolean operators.