SQL练习-用SQL处理数列

​生成连续编号

生成0~99的数。

select d1.digit+(d2.digit *10) as seq from digits d1 cross join digits d2 order by seq;

生成1~888的数。

select d1.digit+(d2.digit *10)+(d3.digit *100) as seq 

from digits d1 cross join digits d2 cross join digits d3 

where d1.digit+(d2.digit*10)+(d3.digits*100) between 1 and 888 

order by seq;

生成视图保存，并从视图中获取数据1~134.

create view sequence(seq) as

select d1.digit+(d2.digit*10)+ (d3.digit*100) as seq 

from digits d1 cross join digits d2 cross join digits d3;

select seq from sequence where seq between 1 and 134;

寻找缺失的编号

寻找缺失的编号。

select seq as'缺失的编号'

from sequence 

where seq between 1 and 12 

and seq not in ( select seq from seqtb1);

代码优化版：

select seq as'缺失的编号'

from sequence

where seq between ( select min(seq) from seqtb1 )

and ( select max(seq) from seqtb1)

and seq not in(select seq from seqtb1);

三个人能坐得下嘛？

上图为火车座位预定情况的表。假设3个人一起去旅行，准备预定这趟火车的车票。寻找三个连续的空座位。

select s1.seat as start_seat,’~’,s2.seat as end_seat

from seats s1,seats s2

where s2.seat=s1.seat+2

and not exists

(select* from seats s3

where s3.seat between s1.seat and s2.seat

and s3.status<>'未预定');

考虑换排问题，查询在同一排的连续的三个空位。

select s1.seat as start_seat,'~',s2.seat as end_seat

from seats2 s1,seats2 s2

where s2.seat=s1.seat+2

and not exists

(select* from seats2 s3

where s3.seat between s1.seat and s2.seat

and s3.status<>'未预定'

or s1.row_id<>s2.row_id);

最多能坐下多少人

按照现在的座位情况，要求座位连续，最多可以坐多少人。

首先创建视图，存储了所有可能序列的视图。

create view sequences(start_seat,end_seat,seat_cnt)

as select s1.seat as start_seat,

s2.seat as end_seat,

s2.seat-s1.seat+1 as seat_cnt

from seats3 s1,seats3 s2

where s2.seat>=s1.seat

and not exists

(select* from seats3 s3

where(s3.seat between s1.seat and s2.seat

and s3.status<>'未预定')

or (s3.seat=s2.seat+1 and s3.status='未预定')

or (s3.seat=s1.seat-1 and s3.status='未预定'));

从试图表中查询最长序列：

select*

from sequences

where seat_cnt=

(select max(seat_cnt) from sequences);

单调递增和单调递减

假设上述的表反应了某公司的股价动态图。

查询股价单调递增的时间区间。

select m1.deal_date as start_date,'~',m2.deal_date as end_date

from mystock m1,mystock m2

where m2.deal_date>m1.deal_date

andnot exists

(select* from mystock m3,mystock m4

wherem3.deal_date between m1.deal_date and m2.deal_date

andm4.deal_date between m1.deal_date and m2.deal_date

andm3.deal_date

andm3.price>=m4.price);