[
  {
    "type": "alter_table",
    "description": "Add unique index on users.email to prevent duplicate email addresses",
    "database": "kiosk_users",
    "check_query": "SELECT INDEX_NAME FROM information_schema.STATISTICS WHERE TABLE_SCHEMA = 'kiosk_users' AND TABLE_NAME = 'users' AND INDEX_NAME = 'uq_users_email'",
    "sql": "ALTER TABLE `users` ADD UNIQUE INDEX `uq_users_email` (`email`)"
  },
  {
    "type": "alter_table",
    "description": "Add unique index on users.username to prevent duplicate usernames",
    "database": "kiosk_users",
    "check_query": "SELECT INDEX_NAME FROM information_schema.STATISTICS WHERE TABLE_SCHEMA = 'kiosk_users' AND TABLE_NAME = 'users' AND INDEX_NAME = 'uq_users_username'",
    "sql": "ALTER TABLE `users` ADD UNIQUE INDEX `uq_users_username` (`username`)"
  }
]