Question

我有2张桌子

First table - userTable

usedID  userName
1          someName
2          someOthername

Second Table - ratingTable

userID ratingValue
1          5
1          3
1          5
1          3
2          5
2          5
2          3
2          5

我需要编写一个SQL查询，它将按升序获取所有userID的次数（5星）

Answer 1

以下是一个例子：

select  u.UserId
,       count(r.ratingValue)
from    userTable u
left join
        ratingTable r
on      u.userID = r.userID
        and r.ratingValue = 5
group by
        u.UserID
order by
        count(r.ratingValue)

如果结果不需要没有任何五星评级的用户，您甚至可以完全省略userTable。

Answer 2

SELECT u.userID, u.userName, COUNT(*) AS ratingCount
    FROM userTable u
        INNER JOIN ratingTable r
            ON u.userID = r.userID
                AND r.ratingValue = 5
    GROUP BY u.userID, u.userName
    ORDER BY ratingCount

Answer 3

我假设您提到5星作为您正在使用的评级系统而不是您只想检索评级为5星的用户。

SELECT u.userName, avg( r.ratingValue ) as averageRating
FROM userTable u
LEFT JOIN ratingTable r ON u.userID = r.userID
GROUP BY u.UserID
ORDER BY avg( r.ratingValue ) desc

这将获得每个用户的平均评分并显示其名称。

userName averageRating
test1   4.5000
test2   1.7500

简单SQL在2个表之间选择查询

3 个答案: