AND, OR, NOT

Boolean operators form the basis of mathematical sets and database logic.

• They connect your seach words together to either narrow or broaden your set of results.
• The three basic boolean operators are: AND, OR, and NOT.

Why use Boolean operators?

• To focus a search, particularly when your topic contains multiple search terms.
• To connect various pieces of information to find exactly what you're looking for.
• Example:
  second creation (title) AND wilmut and campbell (author) AND 2000 (year)

Using AND

Use AND in a search to:

• narrow your results
• tell the database that ALL search terms must be present in the resulting records
• example: athletes AND doping

Using OR

Use OR in a search to:

• connect two or more similar concepts (synonyms)
• broaden your results, telling the database that ANY of your search terms can be present in the resulting records
• example: doping OR drugs

Using NOT

Use NOT in a search to:

• exclude words from your search
• narrow your search, telling the database to ignore concepts that may be implied by your search terms
• example:  doping NOT Olympics

Subject Search

Subject vs Keyword Searching

Subject headings describe the content of each item in a database. Use these headings to find relevant items on the same topic.  Searching by subject headings (a.k.a. descriptors) is the most precise way to search article databases.

It is not easy to guess which subject headings are used in a given database. For example, the phone book's Yellow Pages use subject headings. If you look for "Movie Theatres" you will find nothing, as they are listed under the subject heading "Theatres - Movies."

Keyword searching is how you typically search web search engines.  Think of important words or phrases and type them in to get results.

To find subject headings for your topic:

• Look to see if the database has a thesaurus or subject terms tool to browse for subjects that match your topic (check the Help screens).

Another way to find subject headings:

• Start with a keyword search, using words/phrases that describe your topic.
• Browse the results; choose 2 or 3 that are relevant.
• Look at the Subject or Descriptor field and note the terms used (write them down).
• Redo your search using those terms.
• Your results will be more precise than your initial keyword search.

Truncation

Truncation, also called stemming, is a technique that broadens your search to include various word endings and spellings.

• To use truncation, enter the root of a word and put the truncation symbol at the end.
• The database will return results that include any ending of that root word.
• Examples: 
  teen* = teen, teens, teenage, teenager, teenagers
  genetic* = genetic, genetics, genetically
• Truncation symbols may vary by database; common symbols include: *, !, ?, or #. Check the database's help page for more information.