After using a join, what are the next steps? Do you segregate, update, or insert records?

After performing a join, the typical next steps are to segregate the rows by action, then apply the appropriate DML. Use the METADATA$ACTION column to split into INSERT, UPDATE, DELETE. For INSERTs, perform an INSERT; for UPDATEs, perform an UPDATE; for DELETEs, perform a DELETE. In Snowflake you can do this in a single MERGE: MERGE INTO target USING stream ON target.id = stream.id WHEN MATCHED AND stream.METADATA$ACTION = 'UPDATE' THEN UPDATE SET ... WHEN NOT MATCHED AND stream.METADATA$ACTION = 'INSERT' THEN INSERT ... WHEN MATCHED AND stream.METADATA$ACTION = 'DELETE' THEN DELETE. This keeps the logic in one place and ensures idempotent processing.