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).
A database is a collection of schemas and the schemas contain the tables functions, etc.
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