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我有两个 mysql(AWS Aurora) 数据库表：

--------------------------------
|     Table:deparment          |
--------------------------------
--------------------------------
|    id      |  dept_name      |
--------------------------------
|     d1     |       dept1     |
--------------------------------
|     d2     |       dept2     |
--------------------------------
--------------------------------

-------------------------------------------------
|                Table:employee                 |
-------------------------------------------------
-------------------------------------------------
|   id      |   emp_name       |    dept_id     |
-------------------------------------------------
|   e1      |   Emp 1          |    d1          |
-------------------------------------------------
|   e2      |   Emp 2          |    d1          |
-------------------------------------------------
|   e3      |   Emp 3          |    d1          |
-------------------------------------------------
|   e4      |   Emp 4          |    d2          |
-------------------------------------------------

业务逻辑：多线程可以对Depatment和Employee表进行创建/修改或删除操作。对员工表的任何修改都将导致更新员工 ID

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Java Code with Spring Transaction:

/**
*   Modify Employee
*/
@Transactional(isolation = REPEATABLE_READ)
public void modifyEmployeeByDeptarment(int deptId, int empId Update upd) {
    Department dept = deptDB.getDeparmentForUpdate(deptId); // returns SELECT * FROM department where id = :deptId FOR UPDATE; Row level Lock on dept
    
    Employee employee = empDB.getEmployee(deptId, employee.id); // returns SELECT * from employee where dept_id = :deptId;
    
    employee.setId(newEmpId);
    addUpdate(employee, upd); // This will update in DB
}

/**
*   Delete department with employees
*/
@Transactional(isolation = REPEATABLE_READ)
public void deleteDepartment(int deptId) {
    Department dept = deptDB.getDeparmentForUpdate(deptId); // returns SELECT * FROM department where id = :deptId FOR UPDATE; Row level Lock on dept

    List<Employee> employees = empDB.getEmployeesByDept(deptId); // returns SELECT * from employee where dept_id = :depltId;

    deleteDepartment(dept); // Deletes dept from DB
    deleteEmployees(employees); // Delete all employee for deptId
}
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正如您在此处看到的，对于这两个操作，我在对其相应的员工进行任何更改之前都锁定了部门行。但在少数情况下，我们观察到员工记录存在于我们的数据库中，但没有相应的部门。

有人可以解释这种行为吗？

Spring 框架版本：5.2.0.RELEASE Aurora MySQL 版本：5.7.12

* Note: I changed the isolation level to READ_COMMITED, and everything was working as expected.
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