The postgresql-client-common package provides a structure under which
 multiple versions of PostgreSQL client programs may be installed at
 the same time. It provides a wrapper which selects the right version
 for the particular cluster you want to access (with a command line
 option, an environment variable, /etc/postgresql-common/user_clusters,
 or ~/.postgresqlrc).
 .
 PostgreSQL is a fully featured object-relational database management
 system. It supports a large part of the SQL standard and is designed
 to be extensible by users in many aspects. Its features include ACID
 transactions, foreign keys, views, sequences, subqueries, triggers,
 outer joins, multiversion concurrency control, and user-defined types
 and functions.