Using the dupes change log, answer a point-in-time question: what was each customer's email as of 2026-05-18?
Build the Type-2 versions (ignore NULL emails, collapse consecutive identical emails — same rules as the SCD2 build), then return the version that was in effect on 2026-05-18. Work at day grain: a version whose valid_from date is 2026-05-18 is the one in effect that day (it replaces the previous version). A customer whose first email began after that date has no row.
Sort by customer_id.