为什么不试一试，sql是如此简单

SELECT * FROM teacher WHERE salary <
 (SELECT salary FROM teachear WHERE name='Katherine')

或

SELECT t1.* FROM teacher t1 
  JOIN teacher t2 ON t1.salary < t2.salary AND t2.name='atherine'

更新的答案。
通常名称和总数不能在同一级别显示，如果您想这样做，您可以使用 GROUP_CONCAT 将所有名称合并为一个记录

SELECT count(t.teacher_id) AS count,GROUP_CONCAT(t.name) as names
FROM  teacher t
WHERE t.teacher_id IN
(
SELECT t1.teacher_id FROM teacher t1 
  JOIN teacher t2 ON t1.salary < t2.salary AND t2.name='atherine'
)