[英]Get one row of grouped objects
我有一张包含丈夫对妻子的表。 该表包含每个 realtion 的两行(顺便说一句,性别没有意义。它可能是丈夫 - 丈夫和妻子 - 妻子。只是说)。 意思是,该表可能显示“连接”的两行结果: Wife--Husband
and/or Husband--Wife
该表如下所示:
Id1 | Id2 | ConnectiondID | RelatedConnectionId
-----------------------------------------------------
123 | 333 | FF45 | F421
333 | 123 | F421 | FF45
456 | 987 | F333 | F321
987 | 456 | F321 | F333
我的预期结果是每组只有一个关系:
Id1 | Id2
----------
123 | 333
456 | 987
这实际上非常简单,假设您只想要情侣并且您的ID
值都是唯一的和数字的,并且不需要任何自连接、函数或分组:
declare @t table(Id1 int,Id2 int,ConnectiondID nvarchar(5),RelatedConnectionId nvarchar(5));
insert into @t values(123,333,'FF45','F421'),(333,123,'F421','FF45'),(456,444,'FF46','F422'),(444,456,'F422','FF46'),(789,555,'FF47','F423'),(555,789,'F423','FF47');
select *
from @t
where Id1 < Id2
order by Id1
输出:
+-----+-----+---------------+---------------------+
| Id1 | Id2 | ConnectiondID | RelatedConnectionId |
+-----+-----+---------------+---------------------+
| 123 | 333 | FF45 | F421 |
| 444 | 456 | F422 | FF46 |
| 555 | 789 | F423 | FF47 |
+-----+-----+---------------+---------------------+
如果我正确理解您的问题,您需要在表上执行自ON t1.id1 = t2.id2
例如ON t1.id1 = t2.id2
或ON t1.ConnectionId = t2.RelatedConnectionID
,显然这是ON t1.ConnectionId = t2.RelatedConnectionID
。
为了将其限制为一种方式,在连接谓词上添加一个条件,使得其中一个值小于或大于另一个值; 例如
DECLARE @tbl table( Id1 smallint PRIMARY KEY, Id2 smallint,ConnectiondID char(5),RelatedConnectionId char(5));
INSERT @tbl(Id1,Id2,ConnectiondID,RelatedConnectionId)
VALUES(123,333,'FF45','F421'),
(333,123,'F421','FF45'),
(456,222,'FF45','F421'),
(222,456,'F421','FF45'),
(789,111,'FF45','F421'),
(111,789,'F421','FF45');
SELECT *
FROM @tbl t1
JOIN @tbl t2 ON t2.Id1 = t1.Id2 AND t2.Id1 > t1.Id1;
例如
DECLARE @T TABLE (id1 int, id2 int,ConnectiondID varchar(5),RelatedConnectionId varchar(5) )
INSERT INTO @T (Id1,Id2,ConnectiondID,RelatedConnectionId)
VALUES
(123 , 333 ,'FF45','F421'),
(333 , 123 , 'F421','FF45'),
(2123 , 2333 ,'2FF45','2F421'),
(2333 , 2123 , '2F421','2FF45'),
(3 , 2 , 'AAAA','BBB'),
(2 , 3 , 'BBB','AAAA')
SELECT
a.*
FROM
@t a
WHERE
CASE
WHEN ConnectiondID > RelatedConnectionId
THEN RelatedConnectionId
ELSE NULL
END IS NULL
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