Introduction to users and groups

PostgreSQL distinguishes between users and groups of users: the former represents someone, either a person or an application, that could connect to the cluster and perform activities; the latter represents a collection of users that share some common properties, most commonly permissions on cluster objects.

In order to connect interactively or via an application to a PostgreSQL database, you need to have login credentials. In particular, a database user, a user who is allowed to connect to that specific database, must exist.

Database users are somewhat similar to operating system users: they have a username and an (encrypted) password and are known to the PostgreSQL cluster. Similarly to operating system users, database users can be grouped into user groups in order to make their management easier.

In SQL, and therefore also in PostgreSQL, the concepts of both a single user account and a group of accounts are encompassed by the concept...