Linking terms (also called Boolean operators) form the basis of mathematical sets and database logic.
Why use linking terms?
Use AND in a search to:
The purple triangle in the middle of the Venn diagram below represents the result set for this search. It is a small set using AND, the combination of all three search words.
Be aware: In many, but not all, databases, the AND is implied.
Use OR in a search to:
All three circles represent the result set for this search. It is a big set because any of those words are valid using the OR operator.
Use NOT in a search to:
Databases follow commands you type in and return results based on those commands. Be aware of the logical order in which words are connected when using Boolean operators:
Examples:
Another way to find subject headings:
Subject headings describe the content of each item in a database. Use these headings to find relevant items on the same topic. Searching by subject headings (a.k.a. descriptors) is the most precise way to search article databases.
It is not easy to guess which subject headings are used in a given database. For example, the phone book's Yellow Pages use subject headings. If you look for "Movie Theatres" you will find nothing, as they are listed under the subject heading "Theatres - Movies."
Keyword searching is how you typically search web search engines. Think of important words or phrases and type them in to get results.
Here are some key points about each type of search:
Keywords
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Subjects
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Thanks to MIT Libraries for the use of their content: MIT Libguide: http://libguides.mit.edu/c.php?g=175963&p=1158594