mysql求有薪水差额的任意两位教师

在MySQL中，如果你想要找出薪水有差额的任意两位教师，你可以使用子查询和自连接（INNER JOIN）来实现这个查询。假设我们有两个表，一个是`teachers`表，包含字段`id`, `name`和`salary`，另一个是`salary_history`表，记录了教师的薪水变化，包含字段`teacher_id`（关联教师ID）和`new_salary`。

下面是一个示例SQL查询：

SELECT t1.name AS teacher1_name, t2.name AS teacher2_name, t1.salary - t2.salary AS salary_difference
FROM teachers t1
JOIN (
    SELECT teacher_id, new_salary
    FROM salary_history
) sh1 ON t1.id = sh1.teacher_id
JOIN teachers t2 ON t2.id IN (
    SELECT teacher_id
    FROM (
        SELECT teacher_id, new_salary,
               IF(new_salary > t1.salary, teacher_id, NULL) AS diff_teacher_id
        FROM salary_history sh2
        JOIN teachers t3 ON t3.id = sh2.teacher_id
        WHERE t3.id != t1.id AND (sh2.new_salary > t3.salary OR sh2.new_salary < t3.salary)
    ) subquery
    GROUP BY diff_teacher_id
    HAVING COUNT(*) > 0
)
WHERE t1.id != t2.id;

这个查询首先从`salary_history`中找到每个教师的最新薪水，然后检查是否有其他教师的薪水与其相差。如果有，它将返回两个教师的姓名以及他们的薪水差额。