The Add Column statement allows us to add columns to an existing table in SQL. This is a common statement to use as you are developing your app. In this article, we will learn how to use Add Column in Postgresql.
The basic syntax of Add Column is as follows:
ALTER TABLE [table_name] ADD COLUMN column_name data_type constraint;
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');
Let's do a simple example of adding a middle name column to our employee table.
ALTER TABLE employee ADD COLUMN middle_name varchar(10) null;
By default, this column will be added to the end.
We can also add multiple columns using a comma and multiple add statements.
ALTER TABLE employee ADD COLUMN middle_name varchar(10) null, ADD COLUMN suffix varchar(10) null;