oracle（四）-order by 排序分页重复解决

问题描述：oracle数据库order by排序不唯一，会导致最终的数据排序是不是稳定的，表现出来的结果，就是分页时会重复显示； 症状如下：第2页和第3页有重复的数据。

有问题的sql：

select
        *
    from
        ( select
            u.user_id user_id,
            u.user_name user_name,
            u.mobile1 mobile,
            substr(u.id_no,
            -4) id_no,
            i.industry_name industry_name,
            to_char(su.organ_type) organ_type,
            su.organ_name group_name,
            su.train_date train_date,
            0 assign_status,
            '未分配' assign_status_name 
        from
            szfdc.szfdc_users su 
        join
            sec_users u
                on u.user_id = su.id 
        join
            sec_user_group_rel ug
                on u.user_id = ug.user_id 
        left join
            t_industry i
                on i.organ_type = su.organ_type 
        where
            (
                su.organ_type in (
                    512, 1024,2048
                )
                or su.organ_type is null
            ) 
            and ug.group_id = 10000000313      
        order by
            su.train_date desc nulls last)
    where
        rownum <= 20;

问题解决：建议在 order by 最后，增加 PK 列或 ROWID；

修改后的sql：在order的后面多加了一个u.user_id（主键）进行排序

select
        *
    from
        ( select
            u.user_id user_id,
            u.user_name user_name,
            u.mobile1 mobile,
            substr(u.id_no,
            -4) id_no,
            i.industry_name industry_name,
            to_char(su.organ_type) organ_type,
            su.organ_name group_name,
            su.train_date train_date,
            0 assign_status,
            '未分配' assign_status_name 
        from
            szfdc.szfdc_users su 
        join
            sec_users u
                on u.user_id = su.id 
        join
            sec_user_group_rel ug
                on u.user_id = ug.user_id 
        left join
            t_industry i
                on i.organ_type = su.organ_type 
        where
            (
                su.organ_type in (
                    512, 1024,2048
                )
                or su.organ_type is null
            ) 
            and ug.group_id = 10000000313      
        order by
            su.train_date desc nulls last,u.user_id )
    where
        rownum <= 20;

总结：以后只要遇到排序列可能存在重复的情况下，都多加上一个主键列进行排序