window join in flink sql

[Lu Niu]

Hi, Flink users

How to express multiple stream window join in flink sql? in datastream api,
that's

stream.join(otherStream)
    .where(<KeySelector>)
    .equalTo(<KeySelector>)
    .window(<WindowAssigner>)
    .apply(<JoinFunction>)

(
https://ci.apache.org/projects/flink/flink-docs-master/docs/dev/datastream/operators/joining/
)

For example, in flinksql, how to join two streams in tumbling window and
evaluate a udf joinFunction?

Best
Lu