A表：上学年学生期末考试成绩（只包含参与考试的学生成绩）
B表：上学年学生期末考试补考成绩（包括挂科重考、缺考的学生成绩）
A、B表表结构：STU_NO int （PK）,RESULT int
要得到补考结束后最新的学生成绩，则正确的是
insert into B select * from A left join B on A.STU_NO = B.STU_NO where B.STU_NO is null;
merge into A using B on A.STU_NO = B.STU_NO when not matched then insert (STU_NO,RESULT) values (B.STU_NO,B.RESULT) when matched then update set A.RESULT = B.RESULT;
insert into A select * from B left join A on A.STU_NO = B.STU_NO where B.STU_NO is not null;
insert into A select * from B right join A on A.STU_NO = B.STU_NO where B.STU_NO is null;
