每个孩子的树中的每个父母，祖父母的级别为 1

【问题标题】：every parent in the tree for each child with level for grand parent as 1每个孩子的树中的每个父母，祖父母的级别为 1
【发布时间】：2015-08-10 17:05:42
【问题描述】：

假设我们有以下数据集。

PARENT     CHILD
---------- -----------
S1         S2
S2         S3
S3         S4
S4         S5
S5

我想为每个孩子列出树中的每个父母。例如，

CHILD      PARENT        LEVEL
---------- -----------  ------
S5         S4              4
S5         S3              3
S5         S2              2
S5         S1              1
S4         S3              3
S4         S2              2
S4         S1              1
etc......

【问题讨论】：

标签： sql plsql

【解决方案1】：

with 
    tbl as (select 'S1' as parent,'S2'  as child from dual union all
                    select 'S2' as parent,'S3'  as child from dual union all
                    select 'S3' as parent,'S4'  as child from dual union all
                    select 'S4' as parent,'S5'  as child from dual union all
                    select 'S5' as parent, null as child from dual)
    ,tree as (select connect_by_root(t.child) r
                                    ,t.child,t.parent
                                    ,level l from tbl t
                        where child is not null
                        connect by  prior parent =child)
select r as "CHILD"
            ,parent  as "PARENT"
            ,max(l) over (partition by r) - l + 1 as "LEVEL"
from tree
where r is not null
order by r desc, l

SQL Fiddle

【讨论】：