用于查找表中最长名称和最短名称的SQL查询

Question

我有一个表,其中一列是varchar(city)类型.并希望找到该列中存储的最长和最短值.

select a.city, a.city_length from (select city, char_length(city) city_length 
from station order by city, city_length) a
where a.city_length = (select min(a.city_length) from a) or
      a.city_length = (select max(a.city_length) from a)
group by a.city_length;

有人可以帮忙吗？谢谢

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一个解决方案

select * from (select city, char_length(city) city_length from station order by city, city_length) a group by a.city_length order by a.city_length limit 1;
select * from (select city, char_length(city) city_length from station order by city, city_length) a group by a.city_length order by a.city_length desc limit 1;

Answer 1

我认为我们不需要使用Min和Max函数,也不需要Group by.

我们可以使用以下代码实现此目的:

select top 1 City, LEN(City) City_Length from STATION order by City_Length ASC,City ASC

select top 1 CITY, LEN(city) City_Length from station order by City_Length desc, City ASC

但在这种情况下,它将在2表中显示输出,如果我们想在单个表中组合,那么我们可以使用Union或Union ALL.下面是相同的SQL查询

  select * from (
     select top 1 City, LEN(City) City_Length from STATION order by City_Length ASC,City ASC) TblMin
   UNION
   select * from (
   select top 1 CITY, LEN(city) City_Length from STATION order by City_Length desc, City ASC) TblMax

这里我将select语句嵌套在子查询中,因为当我们使用order by子句时,我们不能直接使用Union或Union ALL,这就是我在子查询中写入它的原因.

Answer 2

最短:

select TOP 1 CITY,LEN(CITY) LengthOfCity FROM STATION ORDER BY LengthOfCity ASC, CITY ASC;

最长:

select TOP 1 CITY,LEN(CITY) LengthOfCity FROM STATION ORDER BY LengthOfCity DESC, CITY ASC;

这适用于HackerRank挑战问题(MS SQL Server).

Answer 3

也许是一个更简单的选择，因为我想您正在寻找有关黑客排名问题的解决方案？限制的增加使我可以更轻松地调试返回错误的问题所在。

SELECT city, length(city) FROM station order by length(city) desc limit 1;

SELECT city, length(city) FROM station order by length(city) asc, city asc limit 1

Answer 4

在MySQL中

(select city, LENGTH(city) cityLength  from station order by cityLength desc,city asc LIMIT 1)
    union all
    (select city, LENGTH(city) cityLength  from station order by cityLength asc,city asc LIMIT 1)

Answer 5

您的查询只需要进行一些调整。根本问题是您不能a像您所做的那样在子查询中使用：

select a.city, a.city_length
from (select city, char_length(city) city_length 
      from station 
     ) a
where a.city_length = (select min(char_length(city)) from station) or
      a.city_length = (select max(char_length(city)) from station);

也就是说，编写查询的更简单方法是：

select s.*
from station s cross join
     (select min(char_length(city)) as mincl, max(char_length(city)) as maxcl
      from station
     ) ss
where char_length(s.city) in (mincl, maxcl);