What is a 'ref()' function used for in dbt?

The 'ref()' function in dbt is used to reference other dbt models for dependency resolution. This is integral to how dbt manages and builds complex data transformation workflows. By using 'ref()', you create a direct link between models, allowing dbt to understand the relationships between them. When one model references another, dbt can automatically determine the order in which to run them based on these dependencies, ensuring that upstream models are built before downstream models.

Using this function not only streamlines the build process but also enhances the maintainability and readability of your SQL code. When you reference a model using 'ref()', dbt resolves the correct schema and table names for each environment (like development or production) based on the configuration specified in your project's profiles, which means less hardcoding and more robustness in your transformations.

This is foundational to dbt's design and workflow, making it a critical aspect for analytics engineers when orchestrating their data transformations.