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
查询所有列：*代表all
select * from sc;查询指定列：直接加属性名
select score from sc;去重：添加‘distinct’
select distinct score from sc;条件查询:添加where,还有like、in、and、or
select score from sc where score>70;排序:order by 属性
select score from sc order by score desc(/asc);分页:前面pageindex，后面pagenumber
select * from sc limit 0,5;
select * from sc limit 5,5;插入
insert into sc (con,sno,score)values(1,11,99);更新
update sc set score = 88 where sn0 = 11;删除
delete from sc where sno = 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;
