AND vs OR
Develop Search Statements
When you search a database, it is important to think about how the database will interpret your search statement. Your search can consist of single words or phrases, or you can combine terms. Single term searches are usually no problem, but if you are searching for a combination of terms, it is important to combine those terms effectively. Whether you are searching a library catalog, an article database, or Google, the same principles apply.
Below are some examples of how key terms, synonyms, and alternate terms can be used to develop effective database search statements. Each example is based on the following research question, key concepts, and synonyms and alternate terms:
- Research question: Does television violence have a negative effect on preschool age children?
- Key concepts: television, violence, preschool children
- Synonyms and alternate terms: TV, kindergarten, nursery school, toddlers
Example 1: Using AND to connect key terms
In the example above, you want to find only that information which includes television and violence and preschool children. If there is information on television and violence which doesn't include preschool children, you probably don't want it. Use AND to focus your search on only the information which includes all your concepts.
Example 2: Using OR to connect synonyms and alternate terms
In the example above, each of the terms represents the same concept: preschool children, so you want to find items that contain one or more of those terms. Some items will have preschool children, some kindergarten, some nursery school, some toddlers. Some items may have 2 or more of your terms.
You may also want to use TV as an alternate term for television. Your search would look like this: television or TV. Use OR to search for items that contain any alternate terms for a key concept.
Example 3: Using both AND and OR in the same search statement
Notice, in the example above, that parentheses are used to group alternate terms used to represent the same concept. Whenever you use both AND and OR in the same search statement, use parentheses to group multiple terms that represent the same or similar concepts. Otherwise, the database will not be able to interpret your search statement correctly.
Quiz: In the search statement above, what term will be found in every item that the search retrieves?
Example 4: Searching for alternate terms with the same base word.
What if you want to find all the variations on the word child: child, children, child's, childish, childhood, etc? You could use OR between each possibility. But you might forget something, such as children's. Most databases allow you to use a shorthand version of OR when the base word is the same. It's called "truncation." In most databases the symbol is the asterisk (*).
You can also use truncation when you want to be sure to get plural and possessive forms of your search terms.
Example 5: Putting it all together
When you need to, you can use AND, OR, parentheses, and truncation to create very complex search statements.
Need more help?
When you need help on your research project, talk to your professor, stop by the Services Desk at the Library, make an appointment to talk with a Reference Librarian, or talk with someone in the Writing Resource Center on your campus.