【2019春招准备：17.sql】

序号	考点	链接	备注（公司、年份）
0	学生成绩基本案例	见下	基本操作
1	查找某用户最近的10条交易记录	见下	招银java1面

0. 学生成绩基本案例

create table stusco (sno int not null,grade int,check (grade>0 and grade<100) );
show tables;
desc stusco;


#添加主键的设置
ALTER TABLE `zzb_test`.`stusco` ADD PRIMARY KEY (`sno`);


insert into stusco (sno,grade) values(1,65);
insert into stusco (sno,grade) values(2,69);
insert into stusco (sno,grade) values(3,41);
insert into stusco (sno,grade) values(5,99);
insert into stusco (sno,grade) values(7,82);
insert into stusco (sno,grade) values(8,70);
insert into stusco (sno,grade) values(10,75);
insert into stusco (sno,grade) values(12,60);
insert into stusco (sno,grade) values(15,79);
insert into stusco (sno,grade) values(22,86);
insert into stusco (sno,grade) values(245,98);
insert into stusco (sno,grade) values(234,92);
insert into stusco (sno,grade) values(113,55);
insert into stusco (sno,grade) values(199,68);
insert into stusco (sno,grade) values(198,77);
insert into stusco (sno,grade) values(236,82);
insert into stusco (sno,grade) values(240,67);
insert into stusco (sno,grade) values(98,72);
insert into stusco (sno,grade) values(137,66);
insert into stusco (sno,grade) values(145,73);


update stusco set grade=95 where sno=5;

# 求学号1,3,5,7,8,10,12,22的学生的成绩
select sno as 学生学号,grade as 学生成绩 from stusco where sno in (1,3,5,7,8,10,12,22);

# 求比上述同学成绩都高的同学学号
select sno from stusco where grade > (select max(grade) from stusco where sno in (1,3,5,7,8,10,12,22));

# 查询成绩评级（分段）
select ss.sno,
	(case
		when ss.grade is null then '缺考'
		when ss.grade <60 then '不及格'
        when ss.grade >=60 and ss.grade< 70 then '及格'
        when ss.grade >=70 and ss.grade<80 then '中'
        when ss.grade >=80 and ss.grade<90 then '良'
        when ss.grade >=90 and ss.grade <100 then '优'
        else '什么鬼分数？'
        end
	)qualification
from stusco ss;

# 统计各个分数段的人数
select
	(case
		when ss.grade is null then '缺考'
		when ss.grade <60 then '不及格'
        when ss.grade >=60 and ss.grade< 70 then '及格'
        when ss.grade >=70 and ss.grade<80 then '中'
        when ss.grade >=80 and ss.grade<90 then '良'
        when ss.grade >=90 and ss.grade <100 then '优'
        else '什么鬼分数？'
        end
	)qualification  
,count(ss.sno) as stuNum from stusco ss 
group by 
case
	when ss.grade is null then '缺考'
	when ss.grade <60 then '不及格'
	when ss.grade >=60 and ss.grade< 70 then '及格'
	when ss.grade >=70 and ss.grade<80 then '中'
	when ss.grade >=80 and ss.grade<90 then '良'
	when ss.grade >=90 and ss.grade <100 then '优'
	else '什么鬼分数？'
	end;
    
# 把学生按照上述的升级评定进行排序，小组内按照学号进行排序
select ss.sno 
from stusco ss order by ss.sno;
group by 
case
	when ss.grade is null then '缺考'
	when ss.grade <60 then '不及格'
	when ss.grade >=60 and ss.grade< 70 then '及格'
	when ss.grade >=70 and ss.grade<80 then '中'
	when ss.grade >=80 and ss.grade<90 then '良'
	when ss.grade >=90 and ss.grade <100 then '优'
	else '什么鬼分数？'
	end as qualification;
    

1.查找某用户最近的10条交易记录

with Sold as (
select row_number() over(partition by 编号 order by 销售时间 desc) rn , * from Sold  
)
select * from Sold  where rn <= 10