Question

在Oracle中显示重复行的理想方法是什么？这里的诀窍是我正在寻找所有行而不仅仅是倍数（重复）。例如，在下面的数据集中：

RSN fname   lname   emailaddress
1   John    Smith   j.smith@system.com
2   John    Smith   j.smith@system.com
3   John    Smith   j.smith@system.com
4   Kevin   Walker  k.walker@system.com
5   James   Kirk    j.kirk@system.com
6   James   Kirk    j.kirk@system.com
7   Kevin   James   k.james@system.com
8   Mike    Jones   m.jones@system.com

我希望返回以下内容：

1   John    Smith   j.smith@system.com
2   John    Smith   j.smith@system.com
3   John    Smith   j.smith@system.com
5   James   Kirk    j.kirk@system.com
6   James   Kirk    j.kirk@system.com

任何帮助？

Answer 1

这是一种方式：

SELECT RSN, fname, lname, emailaddress
  FROM whatever_your_table_is_named t1
 WHERE ( SELECT COUNT(1)
           FROM whatever_your_table_is_named t2
          WHERE t2.fname = t1.fname
            AND t2.lname = t1.lname
            AND t2.emailaddress = t1.emailaddress
            AND ROWNUM < 3
       ) > 1
;

这是另一个：

SELECT t1.RSN, t1.fname, t1.lname, t1.emailaddress
  FROM whatever_your_table_is_named t1
  JOIN ( SELECT fname, lname, emailaddress
           FROM whatever_your_table_is_named
          GROUP
             BY fname, lname, emailaddress
         HAVING COUNT(1) > 1
       ) t2
    ON t1.fname = t2.fname
   AND t1.lname = t2.lname
   AND t1.emailaddress = t2.emailaddress
;

（免责声明：我没有测试其中任何一种。）

Answer 2

此子查询将从表中获取重复项。

    select *
    from (some table)
    where rsn IN (select rsn
                  from (some table) 
                   where fname IN 
                   (select fname
                    from (select fname, count(fname) as dup 
           from (some table)) where dup > 1)

Oracle重复行检测

2 个答案: