Connecting to PostgreSQL Using psql: The Definitive Guide

Introduction to psql

psql is PostgreSQL's powerful command-line client that lets you:

• Execute SQL queries

• Manage databases

• Administer users

• Import/export data

• And much more - all from your terminal!

Whether you're a developer, DBA, or data analyst, mastering psql is essential for working efficiently with PostgreSQL.

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Basic Connection Methods

1. Simple Connection

psql -U username -d database_name -h hostname -p port

Example:

psql -U postgres -d mydb -h localhost -p 5432

2. Connection Using Connection URI

psql postgresql://username:password@hostname:port/database

Example:

psql postgresql://postgres:mypassword@localhost:5432/mydb

3. Connecting Without Specifying Database

psql -U username

This connects to a database with the same name as your username.

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Common Connection Options

Option	Description	Example
-U	Username	-U postgres
-d	Database name	-d mydb
-h	Host address	-h localhost
-p	Port number	-p 5432
-W	Force password prompt	-W
-l	List available databases	psql -l

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Password Authentication Options

1. Interactive Password Prompt

psql -U username -W

(Will prompt for password)

2. Using .pgpass File

Create ~/.pgpass with permissions 600:

hostname:port:database:username:password

Example:

localhost:5432:mydb:postgres:mypassword

3. Environment Variable

export PGPASSWORD="mypassword"
psql -U postgres

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Useful psql Commands

Once connected, try these meta-commands (start with backslash):

Command	Description
\l	List databases
\c dbname	Connect to another database
\dt	List tables
\d tablename	Describe table structure
\x	Toggle expanded display
\timing	Toggle query timing
\i filename.sql	Execute SQL from file
\o filename	Redirect output to file
\q	Quit psql

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Advanced Connection Techniques

1. SSL Connection

psql "sslmode=require host=localhost dbname=mydb user=postgres"

2. Connecting to Amazon RDS

psql -h myinstance.123456789012.us-east-1.rds.amazonaws.com -p 5432 -U myuser -d mydb

3. Tunnel Through SSH

ssh -L 63333:localhost:5432 user@remote-server
psql -h localhost -p 63333 -U postgres

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Troubleshooting Common Connection Issues

Problem: "Connection refused"

• Check if PostgreSQL is running: sudo service postgresql status

• Verify port number (default is 5432)

Problem: "Password authentication failed"

• Check pg_hba.conf for authentication method

• Verify username/password

Problem: "Database does not exist"

• List databases with psql -l

• Create database with createdb

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Conclusion

Mastering psql connections gives you:

• Quick access to PostgreSQL from anywhere

• Scriptable database operations

• Powerful administration capabilities

Pro Tip: Create aliases for frequently used connections in your .bashrc:

alias mydb='psql -U postgres -d mydb -h localhost'

Now you're ready to work with PostgreSQL like a pro! What will you build first?