Once you have identified the keywords and phrases that describe your topic, the next step is to connect them in a logical way that the database will understand - this is accomplished with the use of Boolean operators: AND, OR, NOT.
Databases and many search engines including Google make use of Boolean operators. Understanding how databases interpret your keywords will allow you to execute more specific searches, thereby saving you time while retrieving more relevant results. A database's Help pages will indicate how to construct Boolean searches and which wild cards the database supports.
Boolean operators connect your search words together to either narrow or broaden your set of search results.
AND - narrows a search by finding records that contain all the terms you have entered.
OR - broadens a search by finding records that contain either or all of the terms you have entered
NOT - narrows a search by finding records that contain one term but not another
Use AND in a search to:
Use OR in a search to:
Use NOT in a search to:
Whenever you have more than one Boolean operator, such as AND and OR, in a search statement, it is necessary to separate them with parentheses. This is known as a "nested searching." For example:
("fast food" OR "junk food") AND (obesity OR overweight OR fat) AND (adolescents OR teens OR youth)
Nested searching tells the database the proper order in which to search for the keywords.
Operations enclosed in parentheses are performed first followed by the operators outside the parentheses.
Use phrase searching if you want to ensure that words stay together in a particular order. Phrase searching is accomplished by placing the search terms in quotation marks.
Rules about phrase searching vary from database to database.
Some databases require them (without them an AND would be assumed between each word in your phrase, or worse, the database wouldn't be able to interpret your search); others supply them for you.
The Help Screen of the database you are searching will indicate whether or not quotation marks are required.
In many library databases (including Omni) you can also use a truncation symbol to broaden a search.
Truncation is like a shortcut. Placed at the end of the root of a word (or word stem), a truncation symbol tells the database to search for variant endings of the word, including plurals and singulars.
Truncation symbols vary between databases. In Omni, the truncation symbol is a question mark (?), in many other databases, the symbol is an asterisk (*).
An example of a truncated search in Omni would be:
An example of a truncated search in an article database such as International Bibliography of Theatre and Dance would be:
Omni and the database would interpret the search as theater, theatre, theaters, theatres, theatrical, etc.
Be careful when using truncation as it can produce unintended results. Only truncate back as far as it would be useful and still on topic.