Boolean operators allow you to combine search terms to create effective searches. They are named after George Boole, a 19th-century British mathematician who developed Boolean algebra – a system of logic fundamental to the way computers process information.
Boolean operators, or logical operators, are used to combine, include, or exclude search terms in a search statement. The three main operators are AND, OR, and NOT. Always capitalize them in database searches to ensure they are recognized correctly and not mistaken for regular words.
Use AND in a search to:
EXAMPLE: cats AND dogs
The search returns a small result set, shown by the overlapping yellow area in the Venn diagram, which includes only results containing both cats and dogs.
Please note In many – though not all – library databases, the Boolean operator AND is implied. This means that when you enter two or more words side by side, the database automatically treats them as if AND is placed between them. For example, human rights is interpreted as human AND rights.
Use OR in a search to:
EXAMPLE: cats OR dogs
The result set includes everything within both circles, creating a large set because any item containing at least one of the terms is retrieved.
Use NOT in a search to:
EXAMPLE: cats NOT dogs
The result set includes everything in the first circle except the overlapping area, excluding any records that contain the terms in the second circle.
Watch this 2:15-minute video to learn how Boolean operators can broaden and narrow database searches.
Source: John M. Pfau Library
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