The format function in postgresql allows you to specify a format string when selecting in a query. This function should be familiar to devs who have used the format function in C or related languages. In this article, we will learn how to use format with Postgresql.
The basic syntax of a Format is as follows:
SELECT FORMAT(format_string, ...arguments);
The format string has the following format
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:
Now, navigate to
http://localhost:8081/ to access phpMyAdmin. Then log in with the username
root and pass
Click the SQL tab and you are ready to go.
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: https://dev.mysql.com/doc/sakila/en/. 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'), (10002,'1964-06-02','Bezalel','Simmel','F','1985-11-21'), (10003,'1959-12-03','Parto','Bamford','M','1986-08-28'), (10004,'1954-05-01','Chirstian','Koblick','M','1986-12-01'), (10005,'1955-01-21','Kyoichi','Maliniak','M','1989-09-12');
To start, let's see how we can use the FORMAT function to create a string from values.
Here we use
%s to specify the place of a string.
select format('Hello, %s %s', 'World', 10);
|Hello, World 10|
We can also use the format function to format the full name of our employees.
select format('%s, %s', last_name, first_name) as full_name from employees e;
Let's add the width to our string. We will add 15 characters. Let's add '|' characters so we can see the boundaries.
select format('|%15s|', last_name) as full_name from employees e;
Notice how they are aligned to the right. We can align them left by using the flags option and adding a
select format('|%-15s|', last_name) as full_name from employees e;
Let's end by using the position option to reuse our arguments. We can use
1$ to place our first argument in multiple places. And similar for
2$ to reuse the second argument.
select format('%1$s, %2$s / %2$s, %1$s', last_name, first_name) as full_name from employees e;
|Simmel, Bezalel / Bezalel, Simmel|
|Bamford, Parto / Parto, Bamford|
|Koblick, Chirstian / Chirstian, Koblick|
|Maliniak, Kyoichi / Kyoichi, Maliniak|
|Facello, George / George, Facello|