Combine data from independent SQL services ​

Coordinator DB does not provide a distributed table engine or a remote SQL table function. A query cannot transparently join several remote services. Use an external client to retrieve a defined result from each source, then load compatible local tables for analysis.

Define a consistent boundary ​

Choose the source columns, types and time or key range. Record when each source was read: independent services do not automatically share one transaction snapshot. If a report needs a common cutoff, enforce that cutoff in the extraction process.

Export each source through a supported interface, create explicit destination schemas and import the artifacts. Include a source identifier when different services can use the same local key. Validate row counts and representative values before joining.

Query the gathered data ​

Use ordinary SQL joins and aggregates against the imported tables. Check that key types and null behavior agree rather than converting every field to text. For repeated reports, record completed extraction batches so a retry does not add the same source rows twice.

The local result reflects the extraction boundary, not a continuously synchronized remote view. Refresh it through the same verified client workflow when newer data is required.

See joins guidance, formats and INSERT SELECT.