Lesson 4



Boolean Operators

Now the keywords need to be arranged for searching in an electronic database. The words are already listed by concept, but the relationship between the words and the concepts need to be defined by using Boolean Operators. Boolean Operators are words that are actually computer commands rather than search terms.

Boolean Operators
and
Requires both search terms to be present in retrieved records. Used to combine concepts and to narrow searches.
or
Retrieves records containing just one or both of the search terms. Used to search for synonyms and to broaden a search.
not
Retrieves records which do not contain the search term which follows the operator not. Used sparingly to eliminate unwanted records.

Inserting the Boolean Operators into the list of keywords makes the search look like this:

    (voter turnout or voting or popular vote or voters or electorate)
and   
    (presidential election or electoral college or candidates)

The parentheses around each concept create a nested search. Parentheses are unnecessary in databases where advanced searching is available.

This is a theoretical example. When it comes to actually searching for these terms in an electronic database, they will often need to be broken down into smaller searches. Some databases can handle searching for all of the terms at one time, some cannot.

Examples of shorter search strings:

     (voters or electorate) and candidates
or
     popular vote and electoral college

As a rule, if your searches are retrieving too many results, "and" more terms together (you may also limit the search by date, language or format). If your searches are retrieving too few results, "or" more terms together. Use "not" very sparingly.


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