Connect Postgres Server

• A database is a named collection of SQL objects (“database objects LIKE tables, functions,etc”) that belongs to only one database.
• But there are a few system catalogs eg – pg_database, which belong to a whole cluster and are accessible from each database within the cluster.

Accurately, a database is a collection of schemas
Schemas contain the tables, functions, etc…
hierarchy is Server, database, schema, table

• A client must specify its connection request and the name of the database it wants to connect to. It is not possible to access more than one database per connection.
• But an application is not restricted in the number of connections it opens to the same or other databases.
• Databases arc physically separated and access control is managed at the connection level. If one PostgreSQL server instance is to house projects or users that should be separate and for the most part unaware of each other,
• it is therefore recommendable to put them into separate databases.
• If the projects or users are interraelated and hould be able to use each others resources they should be put in the same database, but possibly into separate schemas.
• Schemas is logical structure for who can access what is managed by the privilege system.

Check whether postgres server is running or not:

[postgres@r1 bin]$ ps -ef|grep postroot  5073  4719  0 14:24 pts/100:00:00 su - postgrespostgres  5074  5073  0 14:24 pts/100:00:00 -bashroot  5149  4996  0 14:27 pts/200:00:00 su - postgrespostgres  5150  5149  0 14:27 pts/200:00:00 -bashpostgres  5188 1  0 14:28 pts/200:00:00 /opt/PostgreSQL/9.3/bin/postgres -D /opt/PostgreSQL/9.3/datapostgres  5189  5188  0 14:28 ?00:00:00 postgres: logger process  postgres  5191  5188  0 14:28 ?00:00:00 postgres: checkpointer processpostgres  5192  5188  0 14:28 ?00:00:00 postgres: writer process  postgres  5193  5188  0 14:28 ?00:00:00 postgres: wal writer process  postgres  5194  5188  0 14:28 ?00:00:00 postgres: autovacuum launcher process postgres  5195  5188  0 14:28 ?00:00:00 postgres: stats collector process postgres  5215  5074  0 14:29 pts/100:00:00 ps -efpostgres  5216  5074  0 14:29 pts/100:00:00 grep post
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Connect The Postgres Server:

[root@r1 data]# su - postgres  [postgres@r1 bin]$ ./psql -p 5432 -U postgres -d postgresPassword for user postgres: psql.bin (9.3.14)Type "help" for help.No entry for terminal type "xterm";using dumb terminal settings.postgres=#
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Conform to connect the right port:

postgres=# select inet_server_port(); inet_server_port------------------5432(1 row)
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Conform to connected database:

postgres=# select current_database(); current_database ------------------ postgres(1 row)
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Conform to connect the right user:

postgres=# select current_user; current_user -------------- postgres(1 row)
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Conform to connected ip address:

postgres=# select inet_server_addr(); inet_server_addr------------------192.168.1.112(1 row)
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Check what Postgresql version you are using:

postgres=# select version(); version --------------------------------------------------------------------------------------------------------- PostgreSQL 9.3.14 on i686-pc-linux-gnu, compiled by gcc (GCC) 4.1.2 20080704 (Red Hat