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<nowiki><pre>
with
DataSet(node,parent)
as
(
select 'A', null union all
select 'F', null union all
select 'B', 'A' union all
select 'C', 'B' union all
select 'E', 'B' union all
select 'E', 'F' union all
select 'G', 'E' union all
select 'D', 'C'
),
Hierarchy( node, parent, level, path )
Hierarchy( node, parent, level, path, isHead, isTail )
as
(
select DataSet.node,
DataSet.parent,
'NULL', -- DataSet.parent,
1 as level,
' → ' || DataSet.node as path
' → ' || DataSet.node as path,
DataSet.parent IS NULL,
NOT EXISTS (SELECT 1 FROM DataSet d WHERE d.parent=DataSet.node)
from DataSet
where DataSet.parent is null
union all
select DataSet.node,
DataSet.parent,
Hierarchy.level + 1 as level,
Hierarchy.path || ' → ' || DataSet.node as path
Hierarchy.path || ' → ' || DataSet.node as path,
DataSet.parent IS NULL,
NOT EXISTS (SELECT 1 FROM DataSet d WHERE d.parent=DataSet.node)
from Hierarchy
join DataSet
on DataSet.parent = Hierarchy.node
)
select *
from Hierarchy
order by path;
|