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PostgreSQL UnderStanding Of Objects

  • A PostgreSQL database cluster contains one or more named databases. 
  • Users and groups of users are shared across the entire cluster and tablespace, but no other data is shared across databases. 
  • Any given client connection to the server can access only the data in a single database, the one specified in the connection request. 
  • Furthermore, database is collection of database objects such as schema, which contains table, view, sequence, functions and other database objects.
  • A database cluster is a collection of databases that is stored at a common file system location (the "data area"). Or A database cluster is a collection of databases that are managed by a single server instance. 
  • It is possible to have multiple database clusters so long as they use different data areas and different communication ports. One postmaster and port per cluster. Accessed from a single “Data Directory”.
  • A database is a named collection of SQL objects (table , function, etc).
Pg_database
A database is a collection of schemas and the schemas contain the tables functions, etc.

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