Working with Chr in Postgres

Intro

Postgresql provides the CHR function to allow us to convert numbers into characters. The function is simple, but helpful in string processing. In this article, we will learn how to use CHR in postgresql.

The Syntax

The basic syntax of a CHR is as follows:

SELECT CHR(num);

Getting Setup

We will be using docker in this article, but feel free to install your database locally instead. Once you have docker installed, create a new file called docker-compose.yml and add the following.

version: '3'
 
services:
  db:
    image: 'postgres:latest'
    ports:
      - 5432:5432
    environment:
      POSTGRES_USER: username
      POSTGRES_PASSWORD: password
      POSTGRES_DB: default_database
    volumes:
      - psqldata:/var/lib/postgresql

  phpmyadmin:
    image: phpmyadmin/phpmyadmin
    links:
      - db
    environment:
      PMA_HOST: db
      PMA_PORT: 3306
      PMA_ARBITRARY: 1
    restart: always
    ports:
      - 8081:80

volumes:
  psqldata:

Next, run docker-compose up.

Now, navigate to http://localhost:8081/ to access phpMyAdmin. Then log in with the username root and pass root_pass.

Click the SQL tab and you are ready to go.

An Example

For a list of codes, we can use the following page: https://en.wikipedia.org/wiki/List_of_Unicode_characters. The decimal column will tell us which number to use in our function.

Let's start with a quick example of selecting a capital A.

select chr(65);

We aren't restricted to the Latin alphabet. Here is an example of using the @ sign.

select chr(174);