Making databases available via the Internet is an expensive proposition for libraries, as most database manufacturing or vending companies have licensing fees dependent on the number of users involved. Of course, local periodical databases use boolean commands and truncation just like any other database. Some databases use, in addition, other commands called proximity commands. While boolean commands are reasonably consistent from database to database, proximity commands vary depending on the database you use. Another kind of special search technique involves using fields .
Field searching can vary from database to database as well.