Searching using Boolean Logic

The Boolean operators are AND, OR and NOT. They are useful when you want to combine different search terms or concepts. It is a good idea to type Boolean operators in capital letters for clarity and readability.

AND is used to combine two or more search terms. In many databases AND is standard; if you do not include an operator, the database will search with AND between the search terms. The more search terms with AND between them, the fewer hits you will get.

An example of a search with AND: child AND diabetes

OR between the search terms will generate hits where both or only one word exists. If you search with OR the number of hits will increase. The OR-operator is useful when you search with various synonyms.

An example of a search with OR: student OR pupil

When various commands are combined, it is important to consider the order in which they should apply. This can often be regulated with the help of brackets. Here are some common examples where AND is the primary operator which combines searches in which the OR operator is included:

Diabetes AND (children OR adolescents OR teenagers)

NOT excludes hits from the search results. In which case, you type NOT before the term you do not want to be included in the search results.

There are exceptions concerning how the Boolean operators work, for example, AND NOT is used in the database Scopus instead of NOT. In the guidelines in the databases, you can read more about how the Boolean operators are used in each database.

An example of a search with NOT: cats NOT dogs.

Tips for Effective Search Strategies (film 03:04)

Clark, S. [@sarah_clark]. (2016, January 20). Online Research: Tips for Effective Search Strategies [Video]. YouTube. https://www.youtube.com/watch?v=LTJygQwYV84. License: CC BY-NC-ND