begin
declare n_avg  number;
select avg(grade) into n_avg from SC;
update SC set GRADE = GRADE*1.05 where grade<n_avg and sid in (select SID from S where SEX=1);
end

select @avgs:=(select avg(grade) from SC);
update SC set GRADE = (GRADE+GRADE*0.05) where GRADE < @avgs and SID in (select SID from S where SEX = 1) ;

The CID in the SC table represents the course ID, so it should be classified by course. For example, the average score of Chinese is 80, then the score of girls whose Chinese score is lower than 80 will be increased by 5%, and then each course will be Follow this logic

Is my understanding correct? If it's right, I'll type the code.