Library Skills Tutorials
Tutorial 3: Keyword Searching Techniques
Using Boolean Operators to Combine Keywords
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Usually one keyword isn't specific enough for your topic. There are a few terms that have special meaning to search engines, based on something called boolean logic. These terms are boolean operators, and they are used as commands, between search terms. When you use one of these operators the system knows that this term has special meaning and applies it. Boolean operators are used to combine terms.
The boolean operators you need to understand to start out are AND and OR.
Combining Keywords Using AND
Focus your search by adding more keywords and joining them with the word "and".
When you use "and" between terms, you specify that both terms must be in every item found.
Examples:
fish and pollution and legislation and ontario
atwood and handmaids
videorecording and teachers and racism
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Using and narrows your search.
You find fewer items, but they're more specific because they all contain all the key concepts.
The words can be in any order and in any searchable place in the record.
Combining Keywords Using OR
Sometimes you need to broaden your search, to include alternate keywords so that you don't miss important items. The boolean operator for this is "or".
Use "or" to say that either term is acceptable.
When you use "or" between search terms, you specify that items
must contain one term or the other, but they don't need both.
Examples:
labour or labor
car or automobile or auto
indian or native or aboriginal or first nation
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Using or broadens your search.
You find more items, because they only need to contain some of the key concepts.
Caution:
Be careful of using both "and" and "or" in the same search request. If you don't put brackets ( ) in the proper spots, the system might search the words in the wrong order, giving inaccurate results.
If you must use both "and" and "or", place brackets around the "or" terms:
crayfish and (river or stream) |
Using Advanced Searches
Not all search engines act exactly the same. Although they are all based on boolean logic and understand boolean operators (AND and OR), they might make certain assumptions.
A search engine might assume AND or OR between search terms.
Or it might make up its own rules. Sometimes + or another symbol is used as an operator.
Find out what's happening by looking for a "Help" button and reading the rules for the database you're using.
Or, you can look for an "Advanced Search" option, which lays it all out for you. Here's Google's advanced search screen:
And this is TOPCAT's advanced search (called a Power Search):
Combining Keywords as Phrases
When you type two words together, a search engine might assume and AND or OR between them:
great lakes = great and lakes
great lakes = great or lakes.
If you want to keep them as a phrase, quotes are often a good idea: "great lakes".
Then it will look for those words together, and not find items with "great" in one place and "lakes" in another (such as My Great Adventures in the Kawartha Lakes).
Other search engines may have different rules, and you need to check under "Help" to see how to keep a phrase together.
The next screen covers Truncation and Wildcards.
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