What function does the always_join parameter serve in Looker?

The always_join parameter in Looker is designed to force specific joins to be included in a query regardless of the fields that users choose to include in their selections. This is particularly useful when certain relationships between tables are always needed for accurate data retrieval, ensuring that the integrity of the dataset is maintained even if users do not explicitly select related fields in their queries.

By using the always_join parameter, developers can ensure that certain joins are always applied to the query, which can be critical for maintaining data context or enforcing business logic. It helps in scenarios where omitting a join could lead to incomplete or misleading results. This parameter is fundamental in modeling relationships in a way that aligns with business requirements and provides a consistent experience for data users.

Other options might describe different functionalities or outcomes that are not associated with the always_join parameter, thereby clarifying why they do not represent its purpose accurately.