Explanation on DBT envronment variable and how to use it [Example included]

In dbt (data build tool), an environment variable is a value that can be set and used throughout the dbt project. These variables can be used to store configuration settings, such as database credentials, and can be accessed and used in various parts of the dbt project, such as in SQL files and in the dbt_project.yml file.

Here’s a breakdown of how environment variables work in dbt:

1. Value Storage: Environment variables are used to store values that are relevant to your dbt project. These values can encompass a wide range of information, but common use cases include database credentials, API keys, file paths, or any other configuration settings that your dbt project relies on.
2. Accessibility: Once you define an environment variable, it becomes accessible throughout your dbt project. This means you can reference and use the variable in different parts of your project, providing a centralized and flexible way to manage settings.
3. Usage in SQL Files: One of the primary ways to use environment variables is within your SQL files. You can reference these variables in your SQL queries, allowing you to parameterize your queries and adapt them based on the values stored in the environment variables. This is useful for maintaining security and flexibility in your SQL code.
4. Usage in dbt_project.yml: Another common location for using environment variables is in the dbt_project.yml file. This YAML configuration file is at the core of your dbt project and defines various project settings. You can use environment variables to parameterize settings within this file, making it easier to share and customize project configurations across different environments (e.g., development, production).

To set an environment variable in dbt, you can use the dbt run command with the –vars flag and a key-value pair in the format key=value. For example, to set the environment variable DB_USER with the value myusername, you can use the following command:

dbt run --vars "DB_USER=myusername"

You can also set environment variables in the dbt_project.yml file by adding a vars key and listing the key-value pairs of the variables you want to set.

name: my_project
version: 0.1.0

vars:
  DB_USER: myusername
  DB_PASSWORD: mypassword

You can access the environment variables in your dbt project by using the {{ var('variable_name') }} syntax. For example, to use the DB_USER environment variable in a SQL file, you would write:

select * from mytable
where user = '{{ var('DB_USER') }}'