The DBI and DBD Perl packages allow Perl programmers to view the many database environments that are on the market in a uniform way. Each supported database environment is implemented as a DBD driver, in much the same way that hardware devices from multiple vendors can be used across CPU platforms. DBD implementations can be obtained by download from the Internet. DBD implementations exist for proprietary products such as Oracle, SQL Server, DB2, etc. and for freely available databases such as MySQL.