Question

朱莉娅要求她的学生创造一些编码挑战。编写查询以打印hacker_id，名称以及每个学生创建的挑战总数。按降序排列挑战总数对结果进行排序。如果多个学生创建了相同数量的挑战，则按hacker_id对结果进行排序。如果多个学生创建了相同数量的挑战且计数小于创建的最大挑战数，则将结果中的学生排除在外。

输入格式

以下表格包含挑战数据：

黑客：hacker_id是黑客的id，而name是黑客的名字。 Hackers Table

挑战：challenge_id是挑战的ID，hacker_id是创建挑战的学生的ID。 Challenges Table

这是我写的查询

select H.hacker_id,H.name,T.challenges_created 
from Hackers H  join 
(SELECT hacker_id , 
       COUNT(Challeneges.challenge_id) as challenges_created 
FROM  Challenges 
GROUP BY hacker_id
HAVING challenges_created >= max(challenges_created) 
) T
on H.hacker_id=T.hacker_id
ORDER BY T.challenges_created desc, H.hacker_id asc

但我收到错误说

消息207，级别16，状态1，服务器WIN-ILO9GLLB9J0，第12行无效列名'challenge_created'。消息207，级别16，状态1，服务器 WIN-ILO9GLLB9J0，第12行无效的列名称'challenge_created'。消息4104，级别16，状态1，服务器WIN-ILO9GLLB9J0，第9行多部分标识符“Challeneges.challenge_id”无法绑定。

Answer 1

Line 9 The multi-part identifier "Challeneges.challenge_id" could not be bound.

您的拼写错误Challenges。

Answer 2

select C.Hacker_id, H.Name, count(challenge_id)
from Hackers H Inner Join Challenges C
ON H.Hacker_Id = C.Hacker_Id
group by C.Hacker_Id, H.Name
having count(challenge_id) not in (select x.ChallengeCount from (  
    select C.Hacker_id, H.Name, count(challenge_id) as ChallengeCount
    from Hackers H Inner Join Challenges C
    ON H.Hacker_Id = C.Hacker_Id
    group by C.Hacker_Id, H.Name
 ) x
where x.ChallengeCount <> (select top 1 count(challenge_id) from Challenges group by hacker_Id order by 1 desc) 
group by x.ChallengeCount
having count(x.challengecount) > 1)
order by 3 desc, 1

Answer 3

SELECT c.hacker_id, h.name, COUNT(c.challenge_id) AS cnt 来自黑客 h，挑战 c 其中 h.hacker_id = c.hacker_id GROUP BY c.hacker_id, h.name 有 count(c.challenge_id) = (SELECT max(COUNT(c1.challenge_id)) FROM Challenges c1 GROUP BY c1.hacker_id) 要么 count(c.challenge_id) NOT IN (SELECT COUNT(c2.challenge_id) FROM Challenges c2 GROUP BY c2.hacker_id 有 c2.hacker_id <> c.hacker_id) ORDER BY cnt DESC, c.hacker_id;

Answer 4

通常，您不能在HAVING子句中引用字段别名而是使用

COUNT(Challeneges.challenge_id)

您也可以尝试

SELECT h.hacker_id, 
       h.name, 
       COUNT(c.challenge_id) AS challenge_count
FROM Hackers h
JOIN Challenges c ON c.hacker_id = h.hacker_id
GROUP BY h.hacker_id, h.name
HAVING challenge_count = 
    (SELECT COUNT(challenge_id) AS count_max
     FROM Challenges
     GROUP BY hacker_id 
     ORDER BY count_max DESC limit 1)
OR challenge_count IN 
    (SELECT DISTINCT c_compare AS c_unique
     FROM (SELECT h2.hacker_id, 
                  h2.name, 
                  COUNT(challenge_id) AS c_compare
           FROM Hackers h2
           JOIN Challenges c ON c.hacker_id = h2.hacker_id
           GROUP BY h2.hacker_id, h2.name) counts
     GROUP BY c_compare
     HAVING COUNT(c_compare) = 1)
ORDER BY challenge_count DESC, h.hacker_id;

在我的代码中，我没有使用别名，因此不会显示任何错误。

来自hackerrank的T-SQL挑战

4 个答案: