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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.
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 search 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.
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.
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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