Working with REPLACE in Postgres

Intro

PostgreSQL provides the REPLACE string function which allows you to replace substrings in a string column. There is a REPLACE statement which works differently, so it is worth noting this is the REPLACE string function. In this article, we will learn how to use REPLACE in PostgreSQL.

The Syntax

The basic syntax of a REPLACE is as follows:

UPDATE
  SET REPLACE(column_name, old_string, new_string)
  WHERE [conditions];

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.

Creating a DB

We start by creating an employee table to work with.

CREATE TABLE employees (
    first_name VARCHAR (50) NOT NULL,
    last_name VARCHAR (50) NOT NULL
);

Next, we can insert some data to replace later on.

insert into employees (first_name, last_name) 
	values 
	('Keith', 'Holliday'),
	('Jon', 'Doe'),
	('Jane', 'Doe');

And, we can preview the data like so.

SELECT * FROM employees;

Replace Example

Now that we are set up, let's update all 'Doe' strings in the last_name with 'Dane'.

UPDATE employees 
SET 
    last_name = REPLACE(
      last_name,
      'Doe',
      'Dane'
    );

Now, let's see our results.

select  * from employees;