List all databases in PostgreSQL psql

Quick bite
—————–

\list

or

\l

to list all databases

\connect {databasename}

to connect to database

\dt

to list tables in current database

Munch
————
psql is interactive frontend for PstgreSQL using which you can connect you postgres database and execute commands and SQL. The commands listed above fall under category meta commands.
More information can be found in psql documentation http://www.postgresql.org/docs/9.3/static/app-psql.html

How to do UPSERT query in PostgreSQL

WITH upsert AS (<update-query-here> RETURNING *) <insert-query-here>  WHERE NOT EXISTS (SELECT * FROM upsert);

<insert-query-here> Should be of form
“INSERT INTO table_name (column1, column2, …) SELECT ‘column_1_value’, ‘column_2_value’, …”
Hence if update query succeeds, insert query wont execute due to WHERE clause.

Thanks to reference http://www.the-art-of-web.com/sql/upsert/

How to check if column exists in MySQL table

SELECT * 
FROM information_schema.COLUMNS 
WHERE 
    TABLE_SCHEMA = 'db_name' 
AND TABLE_NAME = 'table_name' 
AND COLUMN_NAME = 'column_name'

Get System Information in Ubuntu

Quick bite
—————-

uname -a

Munch
———–
uname is command which can be used to get system information on Linux/Unix OS.
Other options can be used to get specific information about current system.
Like
-s, –kernel-name
print the kernel name, 
-r, –kernel-release print the kernel release
-v, –kernel-version print the kernel version
-m, –machine print the machine hardware name
-p, –processor print the processor type
-i, –hardware-platform print the hardware platform
-o, –operating-system print the operating system

For More options http://manpages.ubuntu.com/manpages/raring/man1/uname.1.html

Reset Password for Postgres user in ubuntu

Reference : https://help.ubuntu.com/community/PostgreSQL

In a terminal, type:

sudo -u postgres psql postgres

Set a password for the “postgres” database role using the command:

\password postgres
# It will ask for new password and enter it and start using it :)

Uninstall NodeJS from ubuntu

To uninstall npm

sudo npm rm npm -g

Install Cordova in Ubuntu

To install it from ppa,

sudo apt-add-repository ppa:cordova-ubuntu/ppa
sudo apt-get update
sudo apt-get install cordova-cli
npm install -g cordova

For more information about other installation methods can be found here, https://www.npmjs.com/package/cordova