Question

我有一张表XXXTEST

table XXXTEST (C1 varchar2(50),C2 varchar2(50), dist NUMBER )

使用此示例数据：

('Pune','Mumbai',128);
('Mumbai','Pune',128);
('Pune','Nashik',200);
('Nashik','Pune',200);
('Nashik','Mumbai',250);
('Nashik','Mumbai',250);

我想只选择一次城市组合，即“pune-mumbai”和“mumbai-pune”只能选择一行。

我尝试使用自联接，但这没有帮助。所以，如果您可以提供查询请。

提前致谢。

Answer 1

您可以按字母顺序对城市进行排序，然后使用普通DISTINCT：

select distinct 
   least(c1, c2) as c1, 
   greatest(c1,c2) as c2,
   dist
from XXXTEST

Answer 2

如果c2＆gt; c1，检查切换的组合是否存在，使用NOT EXISTS，切换的c1 / c2列：

select distinct c1, c2, dist
from XXXTEST t1 
where c1 < c2
  or  not exists (select * from XXXTEST t2
                  where t1.c1 = t2.c2 and t1.c2 = t2.c1);

执行为：

SQL>CREATE TABLE XXXTEST (C1 VARCHAR(10),C2 VARCHAR(10), dist integer);
SQL>INSERT INTO xxxtest VALUES ('Pune','Mumbai',128);
SQL>
SQL>INSERT INTO xxxtest VALUES ('Mumbai','Pune',128);
SQL>INSERT INTO xxxtest VALUES ('Pune','Nashik',200);
SQL>INSERT INTO xxxtest VALUES ('Nashik','Pune',200);
SQL>INSERT INTO xxxtest VALUES ('Nashik','Mumbai',250);
SQL>INSERT INTO xxxtest VALUES ('Nashik','Mumbai',250);
SQL>    select distinct c1, c2, dist
SQL&    from XXXTEST t1 
SQL&    where c1 < c2
SQL&      or  not exists (select * from XXXTEST t2
SQL&                      where t1.c1 = t2.c2 and t1.c2 = t2.c1);
C1         C2                dist
========== ========== ===========
Mumbai     Pune               128
Nashik     Mumbai             250
Nashik     Pune               200

                  3 rows found

Answer 3

HIERARCHICAL方法：

SQL> SELECT DISTINCT c1,
  2    c2,
  3    dist
  4  FROM
  5    ( SELECT c1, c2, dist FROM xxxtest CONNECT BY nocycle prior c1 = c2
  6    )
  7  WHERE c1 > c2
  8  /

C1         C2               DIST
---------- ---------- ----------
Pune       Mumbai            128
Nashik     Mumbai            250
Pune       Nashik            200

SQL>

另外，让我们说如果城市之间的距离是唯一的，我想你可以简单地选择DISTINCT距离，而不是让它与城市及其组合变得复杂。

分析方法：

SQL> WITH DATA AS
  2    (SELECT c1,
  3      c2,
  4      dist,
  5      row_number() over(partition BY dist order by dist) rn
  6    FROM xxxtest
  7    )
  8  SELECT c1, c2, dist FROM DATA WHERE rn = 1
  9  /

C1         C2               DIST
---------- ---------- ----------
Pune       Mumbai            128
Pune       Nashik            200
Nashik     Mumbai            250

SQL>

在两列中选择具有相似数据的不同数据

3 个答案: