Guide on Handling Ecto Associations and Embeds

This article by José Valim guides through the intricacies of working with Ecto associations and embeds. It starts with basic definitions and examples of associations, such as 'Post has many comments', detailing how to create the necessary tables and schemas. The guide elaborates on querying associations using preload and joins, and how to manipulate these associations through various methods like `Repo.insert!`, `Ecto.Changeset`, and transactions. The guide then transitions to embeds, showing how data can be embedded in the parent record using databases like PostgreSQL, along with code examples of schema definitions and how to handle them with changesets. The latter portion of the article demonstrates building nested forms in a Phoenix application, managing associations and embeds simultaneously. The post concludes with practical examples of deleting associations, customizing changeset functions, and setting validations.