day 16面试题

查询出没门课程都大于80的学生的姓名

select name from table group by name having MIN(fenshu)>80

编号自增:identity(1,1)

删除除了编号以后，其他信息相同的信息
自动编号 学号 姓名 课程名称 分数
1 200 张三 数学 89
2 200 张三 数学 98
3 201 李四 数学 65

create table sdata.dbo.test(
id varchar(20)
,xh varchar(20)
,name varchar(20)
,ckname varchar(20)
,fs varchar(20)
)

insert into sdata.dbo.test
values(
'1', '200', '张三', '数学',89
)
insert into sdata.dbo.test
values(
'6' , '200','张三', '数学',98
)

insert into sdata.dbo.test
values(
'3', '201','李四','数学',86
)
insert into sdata.dbo.test
values(
'5', '202','王五','数学', 86
)

select * from sdata.dbo.test

用row_number 排序找出大于1的
select ID
--into sdata.dbo.delete_id
from (
select *,
row_number()over(partition by xh,name,ckname,fs order by id asc) as paixu
from sdata.dbo.test) a
where paixu> 1

select * from sdata.dbo.delete_id

--删除大于1的数据
delete from sdata.dbo.test
where exists
(select 1 from sdata.dbo.delete_id
where sdata.dbo.delete_id.id = sdata.dbo.test.id
)

abcd四种 求不同的结果
create table sdata.dbo.name_play(
name varchar(20)
)
insert into sdata.dbo.name_play values('a')
insert into sdata.dbo.name_play values('b')
insert into sdata.dbo.name_play values('c')
insert into sdata.dbo.name_play values('d')

select distinct a.name,b.name from sdata.dbo.name_play a
left join sdata.dbo.name_play b
on a.name<>b.name

不分主客场的话

select distinct a.name,b.name from sdata.dbo.name_play a
inner join sdata.dbo.name_play b
on a.name<b.name

怎么把一个表竖表转化成横表 用转至算
create table sdata.dbo.zhuanzhi(
year varchar(20)
,month varchar(20)
,amount varchar(20)
)

insert into sdata.dbo.zhuanzhi values(
'1992','4','2.4'
)
select * from sdata.dbo.zhuanzhi

select YEAR
,MAX(mon_1) mon_1
,MAX(mon_2) mon_2
,MAX(mon_3) mon_3
,MAX(mon_4) mon_4
into sdata.dbo.heng
from(
select YEAR
,case when month = 1 then amount else null end mon_1
,case when month = 2 then amount else null end mon_2
,case when month = 3 then amount else null end mon_3
,case when month = 4 then amount else null end mon_4
from sdata.dbo.zhuanzhi) a
group by YEAR

--横表转纵表

select YEAR
,mon_1 as amount
,'1' as month
from sdata.dbo.heng
union all
select YEAR
,mon_2 as amount
,'2' as month
from sdata.dbo.heng
union all
select YEAR
,mon_3 as amount
,'3' as month
from sdata.dbo.heng
union all
select YEAR
,mon_4 as amount
,'4' as month
from sdata.dbo.heng