Stream to stream joins are NOT currently supported. This is a regularly requested feature, and I'll look at prioritizing it.

SQLFlow uses duckdb internally for windowing and stream state storage :), and I'll look at extending it to support stream / stream joins.

Could you describe a bit more about your use case? I'd really appreciate it if you could create an issue in the repo describing your use case and desired functionality a bit!

https://github.com/turbolytics/sql-flow/issues

We were looking at solving some of the simplier use cases first before branching out into these more complicated ones :)