2018年11月30日

摘要： 查询平均成绩大于60分的同学的学号和姓名和平均成绩： SELECT B.student_id, student.sname, B.ccc from (select studuent_id,avg(num) as ccc from score GROUP BY student_id HAVING av 阅读全文

摘要： 增 insert into tb1(name,age) values('alex',12),('egg',18); insert into tb2(name,age) select name,age from tb1; 删 delete from tb1 where id>2 and name='a 阅读全文