Database Tutorials

British mathematician George Boole (1815-1864) is well known for the development of the algebraic system known as Boolean algebra (or Boolean logic).  It is a system of mathematical logic that represents relationships between ideas, objects or words, and allows one to organize concepts together in sets.

Boolean algebra was fundamental in the design of modern computers, and its principles have been applied in database and online searching.

Source:

“Boole, George (1815–64).” Funk & Wagnalls New World Encyclopedia. World Almanac Education Group, Inc., 2009.

Many library databases and Web search engines support Boolean searches.  Boolean searching is based on combinations of keywords that are connected by operators.  There are three basic operators: AND, OR, and NOT. These operators are used to limit, widen or define the search strategy.

The Boolean operator AND retrieves every document that contains both of the words specified. Combining search terms with AND in a search narrows the search results, thus retrieving more specific results. To locate information on bell related to chime topics use the search terms:  

bell AND chime

Search processes retrieve every record containing both words bell and chime.  More combinations may be added to narrow the search, such as bell AND chime AND tone.

The Boolean operator OR broadens a search to include documents which have either keyword.  OR is also used when there are common synonyms for a concept or variant spelling of a word.  To find information on heart attack use:

heart attack OR stroke

All documents containing either term heart attack or stroke, or both terms heart attack and stroke will be retrieved, which may result in a large numbers of documents.

 life NOT support

The search results in documents with the keyword life and excludes the term support.

Search terms may be combined in various ways using different combinations of Boolean operators to refine searches. Examples:

oceans OR lakes AND pollution

nurses AND malpractice NOT doctors

children NOT infants AND psychology

The terms may also be placed in a nest.  Search terms and operators included in parentheses will be searched first, then terms and operators outside the parentheses next.  Example:

(ADD OR attention deficit disorder) AND college students

will search for documents containing either the acronym ADD or the phrase attention deficit disorder, then narrow the search results only to those documents which also contain the words college students.