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
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: women AND income
- In many, but not all, databases, the AND is implied.
- For example, Google automatically puts an AND in between your search terms.
- Though all your search terms are included in the results, they may not be connected together in the way you want.
- For example, this search: < university students test anxiety > is translated to: university AND students AND test AND anxiety. The words may appear individually throughout the resulting records.
- You can search using phrases to make your results more specific.
- For example: "university students" AND "test anxiety". This way, the phrases show up in the results as you expect them to be.
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: teenagers OR youth
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
- use NOT sparingly, if at all, because you could end up excluding useful search results (e.g. articles or books that discuss both concepts)
- example: exercise NOT fitness