Boolean operators

Boolean operators are used to combine search terms so that a database, search engine or catalogue understands what you are looking for. This helps to make your search faster and more effective.

The three main Boolean operators are:

  • The AND operator ensures that only results which include all the terms are found. As an example, consider the following question:

    How do stress levels affect health?

    There are two main concepts to be considered: stress and health.

    Using the AND operator, the search is narrowed and only results that include the keywords stress and health are returned. Results that focus on stress but not the effect it can have on health or those that centre solely on health issues are not returned.

    The search (illustrated below) can be entered as follows: stress AND health

    The AND Operator

    This technique can be extended to include more than two keywords. For example, if the above question is adjusted to:

    How do stress levels affect health in men?

    Below are three concepts: stress AND health AND men:

    The AND Operator

    The AND operator can be used to combine any number of keywords and is not
    limited to two or three. Scopus can be used when using the AND operator.

    And

    Transcript of the Video (Word File)

OR

  • The OR operator broadens a search. It can be used when you want to ensure that a number of terms are included in the search. This is particularly useful for using synonyms or related terms in your search.

    For example, the two keywords moon and lunar can be joined together using the OR operator to ensure results include either keywords: moon OR lunar

    The OR Operator

    More than two keywords can be joined using OR. The term elderly, for example, has more than one synonym. A search could be designed as follows: elderly OR geriatric OR aged

    The OR Operator

    Any number of keywords can be connected using OR as seen below:

    Or

    Transcript of the Video (Word File)

NOT

  • The NOT operator is used to exclude a certain keyword and narrows your search results.

    For example, you may be looking for information on nuclear power but not nuclear weapons.

    A search for this can be designed as follows: nuclear NOT weapons

    The NOT Operator

    A number of databases and search engines require the word AND to be added to the front of the NOT operator - check the help section for each individual database.

    In this scenario, the search will be as follows: nuclear AND NOT weapons

    The following video demonstrates how to use NOT in a search via IEEE Xplore and SCOPUS.

    Not

    Transcript of the Video (Word File)

The AND operator combines keywords so that your search results contain every keyword you have chosen - this narrows your results.

The OR operator broadens your search by letting you search for alternate terms, synonyms and related concepts. 

The NOT operator is useful in eliminating records that have an unwanted keyword in them. It narrows your search by exclusion. 

The operator is usually entered in capital letters to distinguish between the keywords.