How to fix the first function?

Question

Oracle

It is not possible to drive the first times as an input parameter for the beginning of labor activity

INSERT INTO TEACHER (HIREDATE)
SELECT HIREDATE
FROM LESSON 
WHERE (SELECT LESSONDATETIME,MIN(LESSONDATETIME) KEEP(DENSE_RANK FIRST ORDER BY LESSONDATETIME)
OVER (PARTITION BY TEACHERPC) FROM LESSON JOIN TEACHER ON TEACHER.PC_TEACHER=LESSON.TEACHERPC)

Answer 1

update teacher t
   set hiredate = (select min(lessondatetime)
                     from lesson l
                    where t.pc_teacher = l.teacherpc)