To find the most relevant sources during a keyword search, it is often necessary to use multiple keywords, to combine them, and to construct the search in a way the database will understand. This requires the use of Boolean operators: AND, OR, and NOT.
Using AND between your search terms narrows your search, meaning that all terms must appear somewhere in a record. For example: "community AND planning" retrieves sources containing information about the the planning of communities.
If your search retrieves few or no results, you may want to broaden it using the Boolean operator OR. Using OR between your search terms means that at least one of the terms must appear in the record.
- If you combine more than two boolean operators, use parentheses to indicate the proper sequence for the database to search them. For example: "(planning or management) and coasts" searches for records containing the words planning OR management, AND also coasts.
- Different databases and catalogs may handle Boolean operators differently. Try using the help function in a database if you need assistance.
The Boolean operator NOT is sometimes incorporated in a search phrase to exclude records containing a certain term. It should be used with caution because it can cause you to unwittingly eliminate relevant sources from your retrieval set.