请问这个哪里错了，成绩小于平均成绩

update sc  set score=score*1.05
where score<(select avg(score) from sc) and sno in (select sno from students where ssex='女');

SQLServer中可以支持这种写法，但是mySql不行的，不能直接把select出的结果集作为条件。
修改为：

update sc  set score=score*1.05
where score<(select score from(select avg(score)score from sc)a) 
and sno in (select sno from (select sno from students where ssex='女')b);

若有帮助，请采纳~