The length function is a string helper function in Postgresql that returns the number of characters or the number of bytes in a string. The length function takes characters, varchar, or text and will return the count for each of these. In this article, we will learn how to use length in Postgresql.
The basic syntax of a LENGTH is as follows:
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');
By default, the LENGTH function will return the number of characters in a string. Let's see a few examples.
select length(' ');
We can also run the length function on our table.
select length(first_name) from employees e;
If we want to get the length of bytes in a string, we can use the
If we run on a unicode character, we see there are 3 bytes instead of 1.
Finally, we can run this on our table.
select octet_length(first_name) from employees e;