select s_id from score group by s_id having c_id not in (select c_id from course where t_id=(select t_id from teacher where t_name='张三'));出现SQL错误怎么修改

可能的原因是子查询返回了多个结果，导致了 SQL 错误。可以将 `=` 操作符替换成 `IN` 操作符来解决这个问题。修改后的 SQL 语句如下所示：

SELECT s_id
FROM score
WHERE c_id NOT IN (
  SELECT c_id
  FROM course
  WHERE t_id = (
    SELECT t_id
    FROM teacher
    WHERE t_name = '张三'
  )
)
GROUP BY s_id;

这个查询语句的作用是查找没有被张三老师教授的课程的学生 ID。