PostgreSQL Cheat

Open source.

Default port: 5432

Get started

http://stackoverflow.com/questions/1471571/how-to-configure-postgresql-for-the-first-time

First you must have an OS user (not a database user) named postgres.

This OS user usually is created when PostgreSQL is installed on Ubuntu via apt-get.

The first login can only be done by the postgres user, so you must do:

sudo -u postgres psql template1

Where template1 is the name of a database which always exists on new installations. If not given, login may fail, since it tries to use a default database with the same name as the username postgres.

This only works if the authentication method for postgres is peer.

peer means that if the OS user named XXX is logged in, then he can automatically login on the database if XXX exists on the database, without having a database password.

The other major method of authentication is md5, which can work for users that don’t exist in the OS and requires a password. This method is safer, but you will have to type more every time.

This can be set under the following configuration file:

sudo vim /etc/postgresql/9.1/main/pg_hba.conf

Your login method is probably being controlled by the user all line in the default config file.

Don’t forget to restart PG after you have edited the configuration file:

sudo service postgresql restart

Using the postgres PostgreSQL user you can create new users as:

sudo -u postgres createuser -deElPrs <my_username>

Role

In PostgreSQL, an user is commonly called a role.

Slash commands

h

Get help:

\h

USE

c

Connect to a database.

\c database_name

SHOW TABLES

dt

List all tables on current database:

\dt

Mnemonic: Database Tables.

DESC

d

Describe table:

\d+

Tools

pgAdmin

pgAdmin is a popular GUI (not browser based) tool to view and edit Pg tables.

Ubuntu 12.04 install:

suto apt-get install -y pgadmin3

Run:

pgadmin3

To view data, select the table, right click then View Data

Internals

Source code:

git clone git://git.postgresql.org/git/postgresql.git

http://www.postgresql.org/docs/9.3/static/git.html

GitHub mirror: https://github.com/postgres/postgres

Coded in C.

Dead rows

http://stackoverflow.com/questions/2596670/how-do-you-find-the-row-count-for-all-your-tables-in-postgres

https://www.postgresql.org/docs/9.1/static/sql-vacuum.html

How many rows are there in each table

http://stackoverflow.com/questions/2596670/how-do-you-find-the-row-count-for-all-your-tables-in-postgres

Estimate:

SELECT schemaname,relname,n_live_tup
    FROM pg_stat_user_tables
    ORDER BY n_live_tup DESC;
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