拼多多笔试题

据说是拼多多的面试题，刚帮人解决的。。。
题目一：

今天帮人看的sql题目,要求见上图：

;with tb_info(CLASS,TEACHER,COURSE) as (

	select '1','A','MATH'

	UNION ALL

	select '1','A','SPORTS'

	UNION ALL

	SELECT '1','B','LANGUAGE'

	UNION ALL

	SELECT '2','A','MATH'

	UNION ALL

	SELECT '3','B','MATH'

	UNION ALL

	SELECT '4','B','LANGUAGE'

	UNION ALL

	SELECT '5','A','SPORTS'

	UNION ALL

	SELECT '6','B','LANGUAGE'

	UNION ALL

	SELECT '6','C','MATH'

)

select t.teacher

       ,t.classNum

       ,count(distinct i.course) as courseNum

       from tb_info i join (

							select teacher,count(*) as classNum from (

												select  teacher,class 

															from tb_info 

																	group by teacher,class

																			) temp 

																			  group by teacher having count(class) > 3

																			) t 

							on i.teacher = t.teacher

							group by t.teacher,t.classNum

							

题目二 求中位数：

declare @freq_num int

;with tb_record(num,freq) as(

	select 1,9

	union ALL

	select 2,2

	union ALL

	select 4,3

	union ALL

	select 6,1

	union ALL

	select 7,2

	union ALL

	select 9,1

)

, temp as (

select num,freq

      ,(select sum(freq)  from tb_record sub where sub.num<=t.num) as ord_num 

      from tb_record t 

)

select  @freq_num = sum(freq) from tb_record

declare @middle_digit int

declare @sql_cmd varchar(max)

set @middle_digit = @freq_num /2

if @freq_num %2 =0

BEGIN

set @sql_cmd = '

;with tb_record(num,freq) as(

	select 1,9

	union ALL

	select 2,2

	union ALL

	select 4,3

	union ALL

	select 6,1

	union ALL

	select 7,2

	union ALL

	select 9,1

)

, temp as (

select num,freq

      ,(select sum(freq)  from tb_record sub where sub.num<=t.num) as ord_num 

      from tb_record t 

)

select sum(num)*1.0/2 from temp where temp.ord_num between '+cast(@middle_digit as varchar)+' and (select top 1 ord_num from temp t where t.ord_num>'+cast(@middle_digit as varchar)+')'

print @sql_cmd

exec(@sql_cmd)

END

;with tb_record(num,freq) as(
	select 1,9
	union ALL
	select 2,2
	union ALL
	select 4,3
	union ALL
	select 6,1
	union ALL
	select 7,2
	union ALL
	select 9,1
)
, temp as (
select num,freq
      ,(select sum(freq)  from tb_record sub where sub.num<=t.num) as ord_num 
      from tb_record t 
)
select sum(num)*1.0/2 from temp 
                      where ord_num between (select max(ord_num)/2 from temp) 
                                    and (select min(ord_num) from temp where ord_num>(select max(ord_num)/2 from temp))