-- Additive: preserves bookings and audit history when a Province removes a unit.
-- Apply after 202609240005_provincial_admin.sql.
ALTER TABLE units
 ADD COLUMN deleted_at DATETIME NULL,
 ADD COLUMN deleted_by BIGINT UNSIGNED NULL,
 ADD KEY idx_units_province_visible(province_id,deleted_at,active),
 ADD CONSTRAINT fk_units_deleted_by FOREIGN KEY (deleted_by) REFERENCES users(id) ON DELETE SET NULL;