Stream conversion functions SQL Function Description TO_APPEND(change_stream_name) Convert the change stream change_stream_name into an append stream. Imagine a change stream user_info has the logical schema with fields: user_id, password, etc, the stream can be processed over the physical schema like below: INSERT INTO password_changed SELECT after.user_id AS user_id FROM TABLE( TO_APPEND(user_info) -- Use the table function to_append() here ) WHERE op='u' AND before.password <> after.password -- Access the fields over the physical schema See more details here. TO_CHANGE(append_stream_name) Convert the append stream append_stream_name into a change stream. You must have a partition key in the append stream in order to convert it into a change stream. When converted, the partition key becomes the change stream’s primary key. Imagine there are two append streams: user_locations that has fields user_id, and location where a new record is created whenever there is an update in a user’s location. user_info that has fields user_id, and name where a new record is created whenever there is an update in a user’s name. We can build a pipeline to output a change stream that allows sink connections to materialize the latest user info with the latest location. To do it, first turn user_locations and user_info into change streams. -- user_location_materialized is a change stream that encodes -- new location per user_id as updates INSERT INTO user_location_materialized SELECT user_id, location FROM TABLE( TO_CHANGE(user_locations) -- user_locations is partitioned by user_id ) -- user_info_materialized is a change stream that encodes -- new name per user_id as updates INSERT INTO user_info_materialized SELECT user_id, name FROM TABLE( TO_CHANGE(user_info) -- user_info is partitioned by user_id ) Then, join user_location_materialized stream with the stream user_info_materialized -- user_info_with_location is a change stream that would emit -- a new update record when a user's name or location changes INSERT INTO user_info_with_location SELECT user_id, user_name, location FROM user_info_materialized ui JOIN user_location_materialized ul ON ui.user_id = ul.user_id See more details here.