PostgreSQL Connect Database

we have already created a database in our previous chapter. You can select or connect database by using following any one methods:

1. Postgresql bin utility:
2. SQL Prompt

1. postgresql bin utility:

You can check available database list using “psql -l”, i.e., :

[postgres@r1 ]$ psql -lPassword: List of databasesName|  Owner | Encoding | Collate |Ctype| Access privileges ------------+----------+----------+-------------+-------------+----------------------- account| u1 | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  musicdb| postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  sales  | u2 | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  temp0copy  | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  temp0copy2 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  template0  | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/postgres  +|  |  | | | postgres=CTc/postgres template1  | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/postgres  +|  |  | | | postgres=CTc/postgres(8 rows)
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You can select your database from command prompt itself at the time when you login to your database First you need to check which is your  host?  using “hostname”. Following is the simple example:

[postgres@r1 ]$ hostnamer1.localdomain
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If you need to log into a Postgres database on a server named “r1”, you can use this Postgres login command:

[postgres@r1 ]$ psql -h r1 -U u2 -d salesPassword for user u2: psql.bin (9.3.14)Type "help" for help.No entry for terminal type "xterm";using dumb terminal settings.sales=>
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If you are logged into the same computer that Postgres is running on you can use the following psql login command, specifying the database (postgres) and username (postgres)

[postgres@r1 ]$ psql -U u2 -d account;Password for user u2: psql.bin (9.3.14)Type "help" for help.No entry for terminal type "xterm";using dumb terminal settings.
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2. SQL Prompt:

sales=> \lList of databasesName|  Owner | Encoding | Collate |Ctype| Access privileges ------------+----------+----------+-------------+-------------+----------------------- account| u1 | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  musicdb| postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  sales  | u2 | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  temp0copy  | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  temp0copy2 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |  template0  | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/postgres  +|  |  | | | postgres=CTc/postgres template1  | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/postgres  +|  |  | | | postgres=CTc/postgres(8 rows)
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Now type the below command to connect/select a desired database, here we will connect to the “account” database:

sales=> \c accountYou are now connected to database "account" as user "u2".account=> \conninfoYou are connected to database "account" as user "u2" on host "r1" at port "5432".account=>
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view the postgres “tname” table Using command Line:

[postgres@r1 ]$ psql -U u2 -d sales -c 'SELECT * FROM tname'Password for user u2:  id | name  ----+-------  1 | nijam  2 | abu  3 | benz  4 | car(4 rows)
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Connect the “sales” database using command Line password

[postgres@r1 ]$ psql -d sales -U u1 -WPassword for user u1: psql.bin (9.3.14)Type "help" for help.No entry for terminal type "xterm";using dumb terminal settings.