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Boolean Operators:
How to Construct Search Statements
There are three logical operators frequently used in computer
database searching: AND, OR, and NOT.
These words when used in the context of database searching are
called Boolean operators. These three words tell the computer how to
combine and search for more than one word at a time.
Logical Operators: AND
The AND operator retrieves those records in the database that contain
all of the terms you entered. In other words, each
record must contain all the words you entered as illustrated in the following
search:
Find: reading comprehension and testing and adults
The computer will retrieve all of the records that have all three terms in
the record. The use of AND will decrease the number of
hits in your search results.
Logical Operators: OR
The OR operator retrieves those records in the database that contain
either or any of the words entered as illustrated in the
following search:
Find: testing or assessment or evaluation
The use of OR will probably increase the number of hits in
your search results.
Logical Operators: NOT
The NOT operator eliminates those records containing a
certain word or phrase.
In searching for information on lunar eclipses, one strategy might be to
search for eclipse NOT solar
The NOT operator should be used cautiously, for you can NOT out
records that would be useful to you. For example, if you want information
on lunar eclipses, if you search eclipse NOT solar, you may eliminate
some useful materials that discuss both solar and lunar eclipses.
However, the NOT operator can be very useful when working with a word that
can be used in two totally different senses. For example, the
word dolphin can mean a sea creature, but it can also be used as the
name of an NFL team. Example:
Find: dolphins not football
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