Using AND, OR, and NOT (Boolean Operators)

The examples on this page illustrate the use of the Boolean operators OR, AND, and NOT (or AND NOT) in indexes, databases, and search engines that support Boolean type searches.
 

In our library catalog, you can use AND, OR, and AND NOT in Subject searches, which look for matches in the title, author, subject headings, and note fields of each catalog record. The most important note field is Contents, which may list individual chapters, essays, short stories, or other parts of a book, anthology or recording.

1. Simple searches with one Boolean operator
2. Parentheses in searches with more than one Boolean operator
3. Truncation
4. Boolean NOT
    

I. Simple searches with one Boolean operator

Imagine that you need to find several books about jazz or blues music for a class assignment. To get an overview of what is available before focusing on some aspect of jazz or blues music, you perform three Keyword searches in an index to periodicals, such as RILM Abstracts of Music Literature.

• jazz OR blues
       This search finds articles that discuss either jazz or blues.
       OR always broadens a search.
   
• jazz AND blues
       This search finds articles that compare jazz and blues.
       AND always narrows a search.
   
• jazz NOT blues
       This search finds articles that are exclusively about jazz.
       NOT always excludes records with the specified term.
       Note: In the library catalog, type jazz AND NOT blues.

jazz

<---- jazz or blues ---->
(The entire turquoise area)

jazz

|

jazz and blues
(Where the sets overlap)

jazz

          |

jazz NOT blues
(Turquoise area)

II. Using parentheses in searches with more than one Boolean operator

Sometimes a focused search must combine several related words for one idea with another word or words, as in the search: (logging or clearcutting) and rainforests.

In this search, we used Boolean OR to combine the related words: logging OR clearcutting. Then we used Boolean AND to combine these words with rainforests. The parentheses ensure that results are what we expect.
 

Parentheses indicate relationships between search terms. They force the computer to process your search terms in the order you intend and to combine them in the way you want. Read more about computer search order below.

Computer search order

A database or search engine processes your search terms from left to right, but it processes all the Boolean AND operators BEFORE processing any Boolean OR operators. To change this order, group synonyms (or terms that belong together) with parentheses. Anything enclosed in parentheses is evaluated first. To see how this works, compare the two hypothetical library catalog searches below:

lacrosse or soccer and history	Retrieves about 80 items Combines soccer and history Retrieves all books about lacrosse This is not what you wanted!
(lacrosse or soccer) and history	Retrieves about 60 items Combines lacrosse or soccer "ANDs" those results with history This is exactly what you wanted!

Of course, you can use more than one OR in a search, as in: (tobacco or smoking) and (cancer or health)

III. Using truncation

If you want to search for part of a word or a whole word that may have several endings, use a "wildcard," commonly an asterisk (*), though some search engines use other symbols.  It will improve search results and save you time. For example:

To Find:	Use:
university or universities	universit*
legislate, legislates, legislator, legislators, legislation, or legislating	legislat*

IV. Using Boolean NOT

How should you use Boolean NOT? Very Carefully!

NOT eliminates all catalog records that contain the term preceded by NOT, but it is a useful tool when a search word has several unrelated meanings. You also can use NOT to exclude some commonly discussed aspect of a subject.

For example, if you are doing a term paper on the epic poem Beowulf, and you keep getting titles about Linux Beowulf Clusters in computing, you could tighten up your search by using NOT or AND NOT. In the library catalog, you could use this subject search to eliminate books about Linux or computing.

beowulf and not (linux or computing)

If you are researching salamanders but do not want to look at anything about newts, you could do this:

salamanders and not newts

However, you should be aware that any book with chapters about both salamanders and newts will be eliminated from your search results. So, NOT is a very risky operator to use in this search!