Search operators, also known as Boolean operators, are words that specify
the relationship between two or more search terms. Search terms can be linked
in a number of ways using the terms and, or, and not.
Using “and” narrows a search. Both of the search terms entered must be
found somewhere in the record, though not necessarily in the same place. For
example, terms may be a part of an author’s name and part of a title. In most
databases, the Boolean operation of “and” is automatically used when two or
more keywords are entered. For example, a nurse is searching for information
about eating disorders. Entering the keywords “anorexia” and “bulimia” will
return only records containing both terms.
Using the Boolean operation of “or” broadens a search. When using this
approach, either search term must be found somewhere in the record. This
is especially helpful when searching synonyms or words with various forms.
Unlike electronic databases, most Internet search engines default to the “or”
operation when two or more keywords are entered. This explains why a search
can retrieve so many irrelevant records. For example, a search strategy of
“anorexia or bulimia” returns records that contain either one or both terms.
Searches can be narrowed by using the Boolean operation of “not.” Using this
operation, a record can be retrieved only if the first search term is present and
the second search term is not present. In the example of eating disorders, enter-
ing keywords “anorexia not bulimia” returns results that contain only anorexia.
Search operators can also be used with Internet search engines. It is essential
to check the help files of the search engine. Some search engines require that
the search operators be typed in all capital letters, some accept two of the three
operators and not the other, and some require the combination “and not” for
the “not” operator.
Another helpful strategy when conducting basic searches is truncation, which
is the ability to retrieve records of search terms that share a common root. In
each database, a symbol of some sort is placed at the end of the group of letters
forming the root search term. The symbol is usually an asterisk, but sometimes
a colon, a question mark, a dollar sign, or a pound sign might be used. Check
the help files to see which symbol is used in the database. Using the longest
root possible increases the accuracy of the search. For example, instead of en-
tering all of the terms “nurse,” “nurses,” and “nursing” in a search, truncation
would replace all three with “nurs*”. The challenge with truncation, however,
is that it is often surprising to find how many words share common roots. In
this example, records that include nursery and nursing home are also retrieved.
The use of wildcards is another strategy that involves substituting symbols
for one or more letters in a search term. Many databases use the question mark
as a wildcard. The help section provides information about how wildcards are
KEY TERMS
Boolean operators:
Words, such
as and, or, and
not, that specify
the relationship
between search
terms
truncation: A
search strategy that
uses a symbol at the
end of a group of
letters that form the
root search term
wildcards: Symbols
substituted for one
or more letters in a
search term4.4 How to Search for Evidence 113