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. Boolean operators connect your search words together to either narrow or broaden your set of search results.
Databases and search engines such as Google make use of Boolean logic. Understanding how databases interpret your keywords will allow you to execute more specific searches, thereby saving you time while retrieving more relevant results. Boolean operators allow you to focus a search, particularly when your topic contains multiple search terms or concepts.
In many databases the Boolean operators are built into the search boxes. A database's Help pages will indicate how to construct Boolean searches and which wildcards the database supports.In the next module, we will apply these search techniques to searching QCAT for books and will briefly look at searching for books in Summon.
Venn diagrams are helpful to visually illustrate how these operators can be used.
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." Here's an example:
("social movements" OR activism) AND (twitter OR facebook OR "social media") AND occupy
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.
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 QCAT, the Library Catalogue) 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 QCAT, the truncation symbol is a question mark (?), in the article database Sociological Abstracts (and many other databases), the symbol is an asterisk (*).
An example of a truncated search in QCAT would be:
An example of a truncated search in an article database such as Sociological Abstracts would be:
The database would interpret the search as teen, teens, teenagers, etc.
Be careful when using truncation as it can produce unintended results. For example, a search for cult* retrieves cult, cults, cultivated, culture, cultures, etc. Only truncate back as far as it would be useful and still on topic.