Boolean Operators

Logical or Boolean operators let you combine terms and decide how your search terms should relate to each other. The most commonly used are AND, OR and NOT, although many databases also allow adjacency operators.

The AND operator finds records containing both or all the terms specified. This option narrows your search thereby decreasing the number of hits, or matching records.

For example, the following will find items containing both the terms "cat" and "dog"

The OR operator finds records which include at least one of the terms specified. This option broadens your search, thereby increasing the number of hits, or matching records. The OR operator is most often used to search for synonyms or terms very close in meaning.

For example, the following finds items containing EITHER "dog" or "cat"

The NOT operator is used to exclude specified terms. It can be very useful but should be used carefully. For example, the following finds items about "cat" but excludes any of those containing the term "dog".