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.
The AND operator retrieves those records in the database that contain all of the words 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.
The OR operator retrieves those records in the database that contain 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
Enter your search terms in the search box to perform a simple search, or click on the 'Advanced Search' link to open the advanced search dialog boxes.
If you enter search terms combined with Boolean operators and do not use parentheses, the search engine assumes your search terms should be combined in a certain order. If you include operators such as AND and OR, it combines them in this order: NEAR PRE AND OR NOT For instance, a search on education AND elementary NOT secondary would be interpreted as (education AND elementary) NOT secondary. So in this case, (education AND elementary) is considered first. This search will return results regarding education with information on elementary but not secondary education.You can also use parentheses to control the order in which your search terms get combined, instead of using the standard operator precedence.