SQL两个表之间的所有可能的循环组合

Question

给出表格：

create table Person( Name varchar(100) )

其中名称对所有人都是唯一的

什么SQL查询可以生成所有可能的n！/（（n-2）！2！）循环组合？

假设Person的基数总是等于4

示例Person = {'Anna'，'Jerome'，'Patrick'，'Michael'）

输出：

Anna, Jerome
Anna, Patrick
Anna, Michael
Jerome, Patrick
Jerome, Michael
Patrick, Michael

任何帮助将不胜感激。谢谢！

这是我的答案（我使用的是oracle SQL）：

select P1.NAME PERSON1, P2.NAME PERSON2
  from (select rownum RNUM, NAME
        from PERSON) P1,
       (select rownum RNUM, NAME
          from PERSON) P2
 where P1.RNUM < P2.RNUM

Answer 1

以下是问题的两种解决方案

SELECT  t1.Name + ',' +  t2.Name AS NamesCombination
FROM Person t1
INNER JOIN Person t2
ON t1.Name < t2.Name

OR（Oracle 11i R2 +）

WITH NamesCombination AS 
( 
    SELECT  1 AS Cntr
            ,Name 
            , CAST(Name AS VARCHAR(MAX))AS NamesCombinations
    FROM Person 
    UNION ALL 
    SELECT  
        nc.Cntr+1
        ,p.Name 
        ,nc.NamesCombinations + ',' +  CAST(p.Name AS VARCHAR(MAX))                      
    FROM Person AS p JOIN NamesCombination nc ON p.Name < nc.Name
    WHERE nc.Cntr < 2  
)
SELECT NamesCombinations
FROM NamesCombination
WHERE Cntr  = 2 

Answer 2

select P1.NAME PERSON1, P2.NAME PERSON2
  from (select rownum RNUM, NAME
        from PERSON) P1,
       (select rownum RNUM, NAME
          from PERSON) P2
 where P1.RNUM < P2.RNUM

Answer 3

请注意，这是TSQL（Sql Server）语法。我知道Oracle支持窗口函数，特别是row_number（），这是此解决方案所必需的。

通过一些试验和错误让它在Oracle中运行起来应该不会太难

select p1.name, p2.name
from 
(
    select name,  row_number() over(order by name) as rownumber 
    from person
) p1
inner join
(
    select name, row_number() over(order by name) as rownumber
    from person
) p2
on p1.name <> p2.name
and p1.rownumber > p2.rownumber
order by 1

row_number为每一行分配一个行号。然后，您需要按照之前的建议加入p1.rownumber＆gt;的附加连接子句。 p2.rownumber