-- One-off migration: adds start_date/end_date to payments. Not read or
-- written by any application code yet — schema-only, for future use.
--
-- MySQL doesn't support IF NOT EXISTS on ADD COLUMN — safe to run once; re-running
-- will error with "Duplicate column name", which is harmless.

ALTER TABLE payments
    ADD COLUMN start_date DATE NULL AFTER payment_date,
    ADD COLUMN end_date   DATE NULL AFTER start_date;
