试用SQL更新语句表达对教学数据库中关系S、SC、C的更新操作:检索所授每门课程平均成绩均大于80分的

INSERTINTOFACULTY(TNAME)SELECTDISTINCTTEACHERFROM(SELECT TEACHER,C．C#．AVG(GRADE) FROM S，SC WHERE SC．C#=C．C#GROUP BY TEACHER，C．C#) ASRESULT(TEACHER,C#,AVG_GRADE)ASX WHFRE80<=ALL(SELECT AVG_GRADE FROM RESULT ASYWHEREY．TEACHER=X ．TEACHER);