Database Searching Guide: The Logical Operators: AND, OR, NOT

Logical Operators


Enable you to group your search terms in the way that relate to one another.  These operators may already be familiar you to from algebra and/or set theory in mathematics.


Narrows your search, by insisting that all of the terms it connects must appear in every record retrieved.  For that reason, it’s often best not to start out a search with too many ANDs, as you may end up with nothing if your search is too demanding.

copyright AND libraries AND “fair use”


Broadens your result by retrieving records containing any of the terms it connects.

chimpanzee OR bonobo OR gorilla

NOT (sometimes AND NOT)

Excludes records containing a specified term.  Can be risky to use in an initial search, and serves best to filter out something you have already seen in a first pass through a database .  For example, in the search below, we can imagine that the researcher has already retrieved references to articles talking about the language of hip-hop, but has decided to do another search using the word “rap,” but does not want to see any of the articles she already viewed in the first search.

language AND rap NOT hip-hop

AND, OR and NOT are usable in most databases.  Many of those resources also assume that two words next to one another are joined by an implicit AND. 

A few databases substitute the phrases “all of these,” “any of these,” and “none of these” for AND, OR, and NOT respectively, usually on pull-down menus next to search boxes.  (Databases of this kind don’t actually permit as flexible a search, but they are unfortunately becoming more popular.)

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