Searching for information on library databases or Internet search engines (click on either link to review the difference between both sources) can often be a frustrating experience. For broad topics, the results obtained from a search can be overwhelming. The following are some techniques for refining your searches to produce more precise results.

Before you begin using a library database or search engine, it is a good idea to write down all the keywords and phrases that describe your topic or the information you are seeking. You should also write down any synonyms or related terms for each keyword.

Boolean searching is based on a system developed by George Boole, a 19th century mathematician. Most library databases support Boolean searching and most Internet search engines support Boolean searching through their advanced search option. The power of Boolean searching is based on connecting keywords with boolean operators. The three basic operators are AND, OR and NOT. Here is how they work:

AND
Type AND between your keywords to narrow your search. The database or search engine will only retrieve those articles or web pages that contain both words. Using AND will decrease the number or hits or articles or web pages in your result list.

Example: school AND crime

Note: Some search engines allow you to type a plus sign (+) in front of a keyword when doing a basic search. This works the same as AND.
Example: +school +crime

OR
Type OR between your keywords to broaden your search. The database or search engine will retrieve those articles or web pages that contain at least one of these words. Using OR will increase the number of articles or web pages in your result list (especially if not used in combination with AND or NOT). Use OR between keywords that are synonyms or have similar meanings.

Example: baby OR infant

NOT
Type NOT before a keyword to exclude that keyword from your search. Using NOT will also narrow your search. Using NOT will decrease the number of articles or web pages in your result list. Be careful when deciding whether you should use NOT in your search. The best use of NOT is when you are searching for a keyword that may have multiple meanings.

Example: saturn NOT car

Note: Some search engines allow you to type a minus sign (-) in front of a keyword when doing a basic search. This works the same as NOT.
Example: +saturn -car

Use parentheses ( ) to keep combination searches in order. In the example below, the database or search engine will retrieve articles or web pages that must contain the word law and at least one of the words in parentheses:

Example: (ecstasy OR mdma) AND law

 

• Boolean Search Examples A Primer on Databases & Catalogs - Unit 4, Online Library Learning Center, Galileo
• Creating a Search Query Research 101 Tutorial, University of Washington Libraries
• Searching Effectively Using AND, OR, NOT Boolean Tutorial, Colorado State University Libraries
• Keyword Searching With Boolean Operators Northwest Missouri State University, Owens Library
• The Fruits of Boolean Searching Northwest Missouri State University, Owens Library

Example: typing teen* will find teen, teens, teenage, teenager, teenagers.

Example: typing cat* will find cat, cats, catalog, catastrophe, catsup, etc.

Note: Check the Help or Tips links available on most library databases and Internet search engines to verify the truncation symbol that should be used for a particular database or search engine (usually an (*) asterisk or (?) question mark). Also, some search engines, such as Yahoo, automatically use truncation without you having to type a truncation symbol.

Example: typing teen will find teen, teens, teenage, teenager, teenagers.

• Truncation Demo Northwest Missouri State University, Owens Librar

Wildcard symbols can be typed in place of a letter or letters within a keyword if you are not sure of the spelling or if there are different forms of the root word.

Example: wom?n will find both women and woman.

Note: Again, check the Help or Tips links available on most library databases and Internet search engines to verify the wildcard symbol that should be used (usually an (*) asterisk or (?) question mark).

Use quotation marks (" ") around keywords to find an exact phrase.

Example: "attention deficit disorder"

Each search engine uses a different relevancy formula that ranks the keywords in your search with where they are found in a web page (ex: title, first paragraph, etc.) as well as how often keywords appear in a web page. The most relevant sites will usually appear on the top of your result list. Most search engine help pages will be vague on how this relevancy formula actually works.

Basic Searching

When performing a basic search on most search engines, all you need to do is to type the keywords that describe your topic with a space in between each word. Most search engines will look for each word separately. In other words, typing two or more keywords with just a space in between each word will be interpreted as if you typed the Boolean Operator AND or OR in between your words. Some search engines interpret a space as AND, some interpret a space as OR and other search engines incorporate both Boolean operators. Most search engine help pages will be vague on how basic searching actually works.

Examples:
teenager smoking prevention
attention deficit disorder

Note:
If you type an exact phrase without quotations (" ") when doing a basic search, most search engines will still look for each word separately. This means your result list will include web pages that not only contain the exact phrase (ex: attention deficit disorder) but also web pages that contain a word or words from the exact phrase appearing separately (ex: attention may appear in one paragraph or sentence and disorder will appear in another paragraph or sentence).

As you try out new library databases or Internet search engines, look for the help or tips links on the home page or initial screen that say things like:

• Help
• Tips
• FAQs
• Advanced searching
• Or ask us here in the library