Let's add a field for details regarding each type of pet. Putting this infor- mation into each pet's record would be a waste of space, but we can add another table to the database, or create a new database entirely. This is only a representation of a database, not necessarily an example of what a database file might look like internally. The resemblance to a Perl hash is not coincidental. In fact, hashes may be tied to DBM files, yielding a simple form of database.
Some databases allow multiple tables in one database.
Simpler databases, like text files and DBMs, do not. We can thus index one of these elements by the text string 'Type' , storing 'dog' in that position. Using similar techniques, we can store and retrieve other related data. As it happens, that is our next topic. Data exchange is a fact of life, however, so DBMS vendors tend to provide ways to export and import data.