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Search and evaluate information

Advanced search techniques

Using good search technique helps you to find relevant information more easily and quickly, i.e. to search effectively. The search functions may look different in the databases but follow they usually follow the same basic principles. The database's help section contains information about how the search functions are designed in that particular database.

Boolean search technique

The Boolean search technique is used in most databases. By combining search terms with the Boolean operators AND, OR, NOT, you can limit or expand the search. Most databases automatically add AND between two keywordsThe Boolean operators are usually written in English and in capital letters. In several databases, you can combine the search terms by making a selection in a drop-down menu next to the search box (see below).


Use AND when all keywords must be included in the document. It narrows the search scope and results fewer hits. E.g. car AND fuel. In many databases, AND is the default.


Use OR when the search term has synonyms or different spellings. Eg car OR vehicle. This expands the search and returns more hits.


Use NOT to exclude keywords that must not appear in the document. e.g. fuel NOT aviation. NOT should be used with caution so as not to exclude relevant documents. Limits the search and returns fewer hits.

Phrase search

When you want to search for several words in a specific order or as a concept, you use phrase search. The phrase is usually denoted in quotation marks (“X Y”), but in some databases you can search for an exact phrase by making a selection from a drop-down menu next to the search box. Phrase search is useful when searching for a specific title. A phrase search narrows the search and returns fewer hits.

Example: "electric vehicle" gives hits where these words are next to each other in that order. Compared to electric AND vehicle, where the two different keywords must appear somewhere in the text, but not necessarily next to each other.


Truncation is used to retrieved different forms of a word such as the singular, plural form or compound words. The word trunk refers to, among other things, to the word stem. The search word is "chopped off" as far as the different forms have a common spelling and the remaining letters are replaced by a truncation character. The truncation character is usually an asterisk (*), but other variants such as a question mark (?) occur. In some databases, the word is automatically truncated. See the database's help section about how to truncate correctly in that particular database. Truncation broadens your search.

Example: engine* returns hits on engine, engines, engineering, engineers...

Be careful about truncating after too few letters as this often results in too many hits that are not relevant.

Example: car* gives hits on cars, carpet, carotin, carbon...


In some databases, you can also truncate inside words, usually to include different spelling variants. This is called masking. Read the help sections for each database to check the search syntax.

Example: organi?ation gives hits on organization and organization, i.e. both British and American spelling.

Other search techniques


To make sure that the database interprets your search correctly, you can use parenthesis in your search query. The keywords in the parentheses are combined first and then combined with other keywords.

Example: (java OR pearl) AND programming - this results in hits with these keyword combinations java + pearl + programming / java + programming / pearl + programming

Field search

Used when you want to limit the search to certain specific fields. Best for a subject search is to select the fields "Title, abstract, keywords". Other fields that you can usually limit to are author, title and year of publication.

Subject terms

When a publication, for example an article or book, is registered in a database, it is assigned a subject keyword that describes the content of the document. These subject keywords vary between subject and database. You will find them under headings such as thesaurus, subject, keywords or index. Searching using the subject words used in the database can easily result in relevant hits.