DO $$
DECLARE
  target record;
BEGIN
  FOR target IN
    SELECT * FROM (VALUES
      ('student_enrollments', 'created_at'),
      ('student_enrollments', 'updated_at'),
      ('student_enrollments', 'removed_at'),
      ('student_groups', 'created_at'),
      ('student_groups', 'updated_at'),
      ('student_group_members', 'created_at')
    ) AS targets(table_name, column_name)
  LOOP
    IF EXISTS (
      SELECT 1
      FROM information_schema.columns
      WHERE table_schema = 'public'
        AND table_name = target.table_name
        AND column_name = target.column_name
        AND data_type = 'timestamp without time zone'
    ) THEN
      EXECUTE format(
        'ALTER TABLE %I ALTER COLUMN %I TYPE TIMESTAMPTZ(3) USING %I AT TIME ZONE ''UTC''',
        target.table_name,
        target.column_name,
        target.column_name
      );
    END IF;
  END LOOP;
END $$;