Using Boolean Logic and Other Techniques to Enhance Search Statements

Boolean logic

Because the Internet is so huge, searches will often provide too many results. Boolean logic, particularly the use of the Boolean operator AND, is the most important technique for limiting results in any database or search engine search. The principal Boolean operators are:

The following table, provided by the University of Washington Information Literacy Learning program, provides examples of the concept of Boolean logic as it relates to search strategies. Boolean logic enables a searcher to create sets of database records, and then to combine these sets.

Click on the links below for a demonstration of each strategy. Select either an animated movie or a static image.

Function		Search Strategy
Narrowing		AND	movie | image
		NOT	movie | image
Broadening		OR	movie | image
		Wildcard	movie | image
Combining		Nesting	movie | image

Note: These files require a Macromedia Flash^® Player.

TIP: Be aware each database and search engine may use Boolean logic in a different way. For example:

• In Yahoo and other search engines you can use the plus sign "+" as a Boolean "AND."
• Some search engines, have pop down lists to help. In HotBot, selecting "All of the words" from the pop down menu is the same as using the Boolean "AND."

Truncation or wildcard

Truncation is a technique that enables a searcher to look for a word and any of its possible endings. This is sometimes called using a "wildcard" as it usually enables the searcher to insert a symbol (like an asterisk * , !, or ?) as a wild card at the end of a word. The symbol used varies depending on where you are searching. Check your help screens. This instructs the computer to look for the root of the word and all alternate word endings. This will expand your search results.

Different databases or search engines may use different symbols for truncation. Common symbols include ? and *

Some databases and search engines will automatically truncate the words entered to look for the plural or an "ing" or "ed" ending.

Phrase Searching

In most search engines, and in many databases, it is possible to search for a phrase, or two or more words appearing next to each other. The most common method for doing this is to surround the phrase with quotation marks. For example, a search for "acid rain" will look for those words in the database, only when they appear next to each other.

Many databases will offer additional methods for limiting and refining search results. Some of these limiters may include:

TIP: Use help screens to determine how these techniques (Boolean, Truncation, and Phrase searching) are used in the database or search engine you are using.

Learning to use the database options

Remember that every database is different, offering different ways to create search statements or use controlled vocabulary. Each database will usually provide help screens to explain how to search effectively within that database.

TIP: Using Boolean logic and other techniques takes practice and of course, all of the techniques will NOT work all of the time. You can only retrieve useful information if the information is IN the database. Always ask for help at the reference desk as needed.

PRACTICE! Use this interactive tutorial to practice constructing search statements!

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