Question

考虑类似StackOverflow的系统的简化表模式：

表格
用户（身份证，姓名）
问题（id，user_id，question）
投票（id，question_id）

我将如何编写

的SQL查询

列出每个用户以及所有问题的总票数，按大多数投票排序？
给定user_id，返回单个用户记录及其总票数？

用户名|总票数（desc）

Answer 1

关于你的第一个问题：

SELECT u.name, COUNT(v.id) AS TotalVotes
    FROM User u
        LEFT JOIN Question q
            INNER JOIN Vote v
                ON q.id = v.question_id
            ON u.id = q.user_id
    GROUP BY u.name
    ORDER BY TotalVotes DESC

关于你的第二个问题：

SELECT u.name, COUNT(v.id) AS TotalVotes
    FROM User u
        LEFT JOIN Question q
            INNER JOIN Vote v
                ON q.id = v.question_id
            ON u.id = q.user_id
    WHERE u.id = @GivenUserId
    GROUP BY u.name

Answer 2

select User.id,
User.name,
count(vote.id) as Votes
from User 
left join Question
on User.id = Question.user_id
left join Vote
on Vote.question_id = Question.id
group by user.id, User.name
order by 3 desc

Answer 3

    SELECT user.name, question.question, count(vote.id) votes
    FROM user
    inner join question on user.id=question.user_id
    inner join vote on question.id=vote.question_id
    GROUP BY user.name, question.question
    ORDER BY votes

用于在类SO系统中显示每个用户的总投票数的SQL查询

3 个答案: