Working with Concat in Postgres



Postgresql provides a few ways to concatenate strings. We can use the concat operator, ||. We also have the CONCAT and CONCAT_WS function. In this article, we will learn how to concatenate strings in Postgresql.

The Syntax

The basic syntax of a CONCAT is as follows:

SELECT CONCAT(string1, string2, ...more_strings);

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'
    image: 'postgres:latest'
      - 5432:5432
      POSTGRES_USER: username
      POSTGRES_PASSWORD: password
      POSTGRES_DB: default_database
      - psqldata:/var/lib/postgresql

    image: phpmyadmin/phpmyadmin
      - db
      PMA_HOST: db
      PMA_PORT: 3306
    restart: always
      - 8081:80


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

In this article, we will need some data to work with. If you don't understand these commands, don't worry, we will cover them in later articles.

We will be using the sample db provided here: However, we will only enter what we need rather than import the whole db.

Next, let's create an film table. This is a slightly simplified version of the sakila database.

CREATE TABLE employees (
    emp_no      INT             NOT NULL,
    birth_date  DATE            NOT NULL,
    first_name  VARCHAR(14)     NOT NULL,
    last_name   VARCHAR(16)     NOT NULL,
    gender      VARCHAR(1),
    hire_date   DATE            NOT NULL,
    PRIMARY KEY (emp_no)

Now, let's enter a few rows

INSERT INTO employees VALUES (10001,'1953-09-02','Georgi','Facello','M','1986-06-26'),

The CONCAT Operator ||

The first way we can concat strings is using the ||. Let's use this to build full names for our employees.

	first_name || ' ' || last_name as full_name
from employees e ;
Bezalel Simmel
Parto Bamford
Chirstian Koblick
Kyoichi Maliniak
George Facello

The CONCAT function

We can accomplish the same using the CONCAT function.

	CONCAT(first_name, ' ', last_name) as full_name
from employees e ;
Bezalel Simmel
Parto Bamford
Chirstian Koblick
Kyoichi Maliniak
George Facello

The CONCAT_WS function

We can accomplish the same using the CONCAT_WS function, but this function also provides more. We can specify a separator then a list of strings. The prevents us from having to type our separate multiple times.

To get a sense of this, let's also add in the birth date to concatenate. We will use a space as the separator. Notice, in the previous example, we would have needed to type space multiple times.

	CONCAT_WS(' ', first_name, last_name, birth_date) as full_name_and_date
from employees e;
Bezalel Simmel 1964-06-02
Parto Bamford 1959-12-03
Chirstian Koblick 1954-05-01
Kyoichi Maliniak 1955-01-21
George Facello 1953-09-02