BeepZone/backend/database/dev/update_003_make_zone_code_required_unique.sql

-- Make zone_code required and unique
-- This ensures data integrity for audits and lookups

-- First, modify the column to be NOT NULL
ALTER TABLE `zones` MODIFY `zone_code` VARCHAR(50) NOT NULL;

-- Then add the unique constraint
ALTER TABLE `zones` ADD UNIQUE KEY `unique_zone_code` (`zone_code`);