What database conditions do federated joins require?

Federated joins in Looker have specific requirements that must be met to ensure the joins work effectively across different data sources.

When a join is federated, the data sources being joined need to share certain characteristics. Firstly, they must use the same SQL dialect, which ensures that the syntax and functions used in the database queries are compatible. Different databases may have varying SQL dialects, and using mismatched dialects could lead to errors or difficulties in executing the queries.

Additionally, for federated joins to function properly, the data sources should reside on the same physical machine or at least be within the same network environment. This proximity minimizes latency issues and improves performance, which is critical for real-time data analysis and reporting.

Lastly, both databases must be accessible from the same connection in Looker. This means that the connection settings in Looker must allow access to both data sources simultaneously. If the databases are not part of the same connection, Looker will not be able to perform the federated join as it would lack the necessary credentials or pathways to access one of the datasets.

Therefore, the correct choice encompasses all these conditions, indicating that for federated joins to work appropriately, the involved datasets must meet all the specific requirements related to SQL dialect,