When using a database, you cannot type a sentence or a question in the search box like you can on the Internet and expect to find anything useful. You have to search using keywords. How do you know what keywords to search with? Language is rich and fertile. There is generally more than one way to express an idea or concept. Let's say you are looking for information on women and sports and you specifically want to explore whether sports participation has an effect on one's self-esteem. What words would you use to convey this multi-faceted concept? When starting to research a topic, you would:
For example, if I wanted to pick keywords for my topic of women and the effect of sports on their self-esteem, I would pick out the main concepts and use them as my keywords and then try to pick out a synonym or two:
|CONCEPT 1||CONCEPT 2||CONCEPT 3|
The keywords you come up with are what you will use to search the database. Once you do an initial search with the keywords you came up with, you can then review the results and select an article that matches what you are looking for. Within the record of that article will be a list of what subject terms were applied to the article. This will tell you what formal subject terms that database uses for your topic.
For example, some databases use the term American Indian and not Native American, or petroleum and not oil. By searching with the formal subject term the database uses for your topic, you can be sure of pulling up all the material on the subject, no matter what terms the individual authors used in the various articles.
Once you have your topic picked out and have chosen the keywords you are going to use to search for books in a library catalog or articles in a library database, you can use Boolean Operators (AND, OR, NOT) to build effective search statements that will help insure that you are asking for exactly what you want and getting the best results from your search efforts.
AND is used to combine two or more concepts. Let's say you want to investigate the relationship between use of cell phones and traffic accidents. There are lots of articles on cell phones and lots of articles about traffic accidents.
But when you combine the two concepts with AND – cell phones AND traffic accidents – you narrow or limit your search to only those articles that discuss both.
The circle on the left represents every article that discusses any aspect of cell phones, while the circle on the right represents every article that discusses anything about traffic accidents. The small part in the center, where the two circles overlap, is the part that represents articles that discuss both concepts. You can see that this is a much smaller number of records. AND narrows the search. Use AND when your search retrieves too many records and you need to limit your search.
OR is used to combine synonyms or words that are acceptable substitutes for each other. For example, in the search above, I could ask for "traffic accidents" OR "automobile accidents." Either term is equally acceptable to me. When you use OR, you are telling the computer that you will accept either (or both) terms in every document that is retrieved.
OR expands your search and you will retrieve more records. (Memory aid: "OR is more.")
In the diagram above, your search would retrieve everything in the orange circle, everything in the yellow circle, and everything in the overlapping center circle. Use OR when your search retrieves too few records and you need to broaden your search.
NOT is generally used to weed out those "false hits". If your search returns a lot of records that are unrelated to your search need, you can refine the search using NOT to eliminate the records you don't want. For example, if you are searching for information on the python (a snake), and you keep getting information on "Monty Python," the British comedy, you could state your search as "python NOT Monty." (Or you could add the word snake to your search.) It is best to run your search first and see what you get before you use NOT to refine a search. You will use the AND and the OR operators much more often than you will use the NOT operator.
|AND||use AND to combine two or more concepts||narrows search; fewer results|
|OR||use OR to include synonyms||expands search; more results|
|NOT||use NOT to exclude unwanted terms||narrows search; fewer results|
When you combine AND and OR statements in a search, you should enclose the OR statements in parentheses. This is called "nesting," and is done to tell the computer to search those terms first (similar to using parentheses in mathematical equations to indicate the sequence of operations to be performed).
(women OR girls OR females) AND (sports OR athletics) AND (self-esteem OR self-confidence)
Nesting makes a difference in the results so be sure to enclose your OR statements in parentheses.