Question

编辑我拥有的SQL版本（mysql 5.7）不支持row_number() ...我可以使用哪种替代方法？

我研究发现，使用row_number()可以在哪里应用查询...我要检查的列是user_id racid和ios < / p>

SELECT 
    ur.user_id,
    u.racid,
    u.fname,
    u.lname,
    u.email,
    u.last_login,
    ur.role_id,
    r.name AS role_name,
    i.device_token AS ios,
    dg.group_name,
    dg.ad_group,
    a.device_token AS android
FROM
    users AS u
        LEFT OUTER JOIN
    user_roles AS ur ON u.id = ur.user_id
        LEFT OUTER JOIN
    roles AS r ON ur.role_id = r.id
        LEFT OUTER JOIN
    ios_tokens AS i ON u.racid = i.racf_id
        LEFT OUTER JOIN
    android_tokens AS a ON u.racid = a.racf_id
        LEFT OUTER JOIN
    dashboard_groups AS dg ON dg.role_id = r.id

加入后的当前表

user_id, racid, fname, lname, email, last_login, role_id, role_name, ios, group_name, ad_group, android

Answer 1

您可以尝试在下面将其用于mysql 8 +

select * from 
(SELECT 
    ur.user_id,
    u.racid,
    u.fname,
    u.lname,
    u.email,
    u.last_login,
    ur.role_id,
    r.name AS role_name,
    i.device_token AS ios,
    dg.group_name,
    dg.ad_group,
    a.device_token AS android,row_number() over(partition by ur.user_id,u.racid,i.device_token order by ur.user_id,
    u.racid,i.device_token) as rn
FROM
    users AS u
        LEFT OUTER JOIN
    user_roles AS ur ON u.id = ur.user_id
        LEFT OUTER JOIN
    roles AS r ON ur.role_id = r.id
        LEFT OUTER JOIN
    ios_tokens AS i ON u.racid = i.racf_id
        LEFT OUTER JOIN
    android_tokens AS a ON u.racid = a.racf_id
        LEFT OUTER JOIN
    dashboard_groups AS dg ON dg.role_id = r.id
)X where rn<>1

或者低于8版本的Mysql，您可以尝试以下

select * from 
( SELECT 
            ur.user_id,
            u.racid,
            u.fname,
            u.lname,
            u.email,
            u.last_login,
            ur.role_id,
            r.name AS role_name,
            i.device_token AS ios,
            dg.group_name,
            dg.ad_group,
            a.device_token AS android,
             @row_number:=CASE
            WHEN @user_id = ur.user_id and @racid = u.racid and @evicetoken = i.device_token  THEN @row_number + 1
            ELSE 1
        END AS num,
        @user_id :=ur.user_id, @racid = u.racid, @evicetoken = i.device_token 
        FROM
            users AS u
                LEFT OUTER JOIN
            user_roles AS ur ON u.id = ur.user_id
                LEFT OUTER JOIN
            roles AS r ON ur.role_id = r.id
                LEFT OUTER JOIN
            ios_tokens AS i ON u.racid = i.racf_id
                LEFT OUTER JOIN
            android_tokens AS a ON u.racid = a.racf_id
                LEFT OUTER JOIN
            dashboard_groups AS dg ON dg.role_id = r.id,
        (SELECT @user_id:=0,@racid=0,@evicetoken=0,@row_number:=0) as t
)X where num<>1

Answer 2

这与删除重复的行无关，但是如果您需要单个表中多列的唯一性，则可以对多列使用唯一索引。如果不是，那么请忽略此内容。

ALTER TABLE `users` ADD UNIQUE `unique_index`(`col1`, `col2`, `col3`);

How do I specify unique constraint for multiple columns in MySQL?

MYSQL删除基于3列的重复行

2 个答案: