写在前面

创建表‘sc’代表学生成绩单；
创建属性‘con’代表‘课程’，容我失策‘cno’写成‘con’；
创建属性‘sno’代表学生的学号；
创建属性‘score’代表分数；

基础篇

1. 查询所有列：*代表all
   select * from sc;

2. 查询指定列：直接加属性名
   select score from sc;

3. 去重：添加‘distinct’
   select distinct score from sc;

4. 条件查询:添加where,还有like、in、and、or
   select score from sc where score>70;

5. 排序:order by 属性
   select score from sc order by score desc(/asc);

6. 分页:前面pageindex，后面pagenumber
   select * from sc limit 0,5;
   select * from sc limit 5,5;

7. 插入
   insert into sc (con,sno,score)values(1,11,99);

8. 更新
   update sc set score = 88 where sn0 = 11;

9. 删除
   delete from sc where sno = 10;

10. as
    select distinct a.sno from
    (select sno,score from sc where con = 1) a,
    (select sno,score from sc where con = 2)b
    where a.score > b.score
    order by a.sno
    limit 0,10;