Working with Update Join in Postgres



The UPDATE statement with the Join allows us to change rows in a table based on joined data. Often you will want to connect two tables and updated based on conditions form the joined result. In this article, we will learn how to use UPDATE Join in PostgreSql.

The Syntax

The basic syntax of UPDATE JOIN is as follows:

UPDATE [table_name]
  JOIN [table2_name]
  column1  = value1,
  column2 = value2

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)
CREATE TABLE salaries (
    emp_no      INT             NOT NULL,
    salary      INT             NOT NULL,
    from_date   DATE            NOT NULL,
    to_date     DATE            NOT NULL,
    FOREIGN KEY (emp_no) REFERENCES employees (emp_no) ON DELETE CASCADE,
    PRIMARY KEY (emp_no, from_date)

Now, let's enter a few rows

INSERT INTO employees VALUES (10001,'1953-09-02','Georgi','Facello','M','1986-06-26'),
INSERT INTO salaries VALUES (10001,60117,'1986-06-26','1987-06-26'),

An Example

Let's start an example where we update an employee name. Notice that we use the WHERE clause to ensure we update the correct row.

UPDATE employees
	JOIN salaries AS s ON employees.emp_no = s.emp_no
SET first_name = 'Alex',
	last_name = 'Tam',
	s.salary = 8000
WHERE s.salary < 70000;

We often want to update only a single row or multiple rows based on a condition. However, it is worth noting that we can update all rows in the db if we leave off the WHERE clause.

This will update all employees and salaries.

UPDATE employees
	JOIN salaries AS s ON employees.emp_no = s.emp_no
SET first_name = 'Alex',
	last_name = 'Tam',
	s.salary = 8000