oracle表关联层级树查询

select level
      ,lpad(' ', (level - 1) * 20, ' ') || t.fk_table as node_name --节点名称（带缩进）
      ,t.fk_name
      ,t.fk_table
      ,t.pk_name
      ,t.pk_table
  from (select null           as fk_name
              ,uta.table_name as fk_table
              ,null           as pk_name
              ,null           as pk_table
          from user_tables uta
         where not exists (select 1
                  from user_constraints uc
                 where uc.constraint_type = 'R'
                   and uc.table_name = uta.table_name)
        union all
        select a.constraint_name as fk_name
              ,a.table_name      as fk_table
              ,b.constraint_name as pk_name
              ,b.table_name      as pk_table
          from user_constraints a
              ,user_constraints b
         where a.constraint_type = 'R'
           and b.constraint_type = 'P'
           and a.r_constraint_name = b.constraint_name) t
start with t.pk_table is null
connect by prior t.fk_table = t.pk_table
--
;

从父节点查询子节点
start with t.pk_table is null
connect by prior t.fk_table = t.pk_table

从子节点查询父节点
start with t.fk_table = 'ASSIGN'
connect by prior t.pk_table = t.fk_table



--alias as child and parent

select level
      ,lpad(' ', (level - 1) * 20, ' ') || t.child_table as node_name --节点名称（带缩进）
--      ,t.node_name
      ,t.child_table
--      ,t.pk_name
      ,t.parent_table
  from (select null           as node_name
              ,uta.table_name as child_table
              ,null           as pk_name
              ,null           as parent_table
          from user_tables uta
         where not exists (select 1
                  from user_constraints uc
                 where uc.constraint_type = 'R'
                   and uc.table_name = uta.table_name)
        union all
        select a.constraint_name as node_name
              ,a.table_name      as child_table
              ,b.constraint_name as pk_name
              ,b.table_name      as parent_table
          from user_constraints a
              ,user_constraints b
         where a.constraint_type = 'R'
           and b.constraint_type = 'P'
           and a.r_constraint_name = b.constraint_name) t
start with t.parent_table is null
connect by prior t.child_table = t.parent_table
--
;