匹配 2 列，但在 SQL 中循环匹配所有替代项

Question

我的数据是这样的

Col_X	Col_Y
a	b
b	c
c	d
d	e
f	g
t	y
y	r
q	w
n	米
米	k
米	z

我的最终目标簇表应该是这样的：

集群
abcde
fg
nmkz
qw
蒂尔

我的伪数据

select 'a' as x, 'b' as y union all
select 'b' as x, 'c' as y union all
select 'c' as x, 'd' as y union all
select 'd' as x, 'e' as y union all
select 'f' as x, 'g' as y union all
select 't' as x, 'y' as y union all
select 'y' as x, 'r' as y union all
select 'q' as x, 'w' as y union all
select 'n' as x, 'm' as y union all
select 'm' as x, 'k' as y union all
select 'm' as x, 'z' as y 

Answer 1

通过一个小准备来递归收集所有兄弟，请注意，如果没有排序列，这部分可能从一个执行到另一个执行是随机的：

with data(x, y) as (
    select 'a' as x, 'b' as y union all
    select 'b' as x, 'c' as y union all
    select 'c' as x, 'd' as y union all
    select 'd' as x, 'e' as y union all
    select 'f' as x, 'g' as y union all
    select 't' as x, 'y' as y union all
    select 'y' as x, 'r' as y union all
    select 'q' as x, 'w' as y union all
    select 'n' as x, 'm' as y union all
    select 'm' as x, 'k' as y union all
    select 'm' as x, 'z' as y 
),
adata(x, y) as (
    select x, listagg(y, '') as y from data d group by x
)
,cte(l, x,y,c,r) as (
    select 1, x, y, x, x
    from adata d
    where not exists(select 1 from adata d1 where d1.y = d.x)

    union all
    
    select c.l + 1, d.x, d.y, c.c || d.x, c.r
    from cte c
    join adata d on d.x = c.y 
)
select c from (
    select r, c || y as c, row_number() over(partition by r order by length(c || y) desc) as rn
    from cte 
)
where rn = 1
;

abcde
nmkz
qw
fg
tyr