Oracle 12c DB查看错误 - ORA-01810：格式代码出现两次

Question

以下是我的观点：

CREATE OR REPLACE VIEW STUDENT_DETAILS AS
SELECT 
          COALESCE(Dept.deptname, stu.deptname,' ') AS deptname,
          CASE WHEN college.JOIN_DATE IS NULL THEN ' ' ELSE TO_DATE(college.JOIN_DATE, 'dd-MM-yyyy') || ' '  END AS JOINDATE
FROM 
          College_register college
             LEFT JOIN Department dept ON college.stuid=dept.stuid 
             LEFT JOIN student stu ON college.stuid=student.stuid;

当我执行以下查询时，我收到错误“ORA-01810：格式代码出现两次”

SELECT * FROM STUDENT_DETAILS;

但是当我执行如下（只是没有视图的选择查询）时，我不看到上述错误。

SELECT 
          COALESCE(Dept.deptname, stu.deptname,' ') AS deptname,
          CASE WHEN college.JOIN_DATE IS NULL THEN ' ' ELSE TO_DATE(college.JOIN_DATE, 'dd-MM-yyyy') || ' '  END AS JOINDATE
FROM 
          College_register college
             LEFT JOIN Department dept ON college.stuid=dept.stuid 
             LEFT JOIN student stu ON college.stuid=student.stuid;