[Oracle] How to obtain the root node of a tree using Oracle9i

How to obtain the root node of the tree from Oracle9i

 

In Oracle 10 Gb, we can useSys_connect_by_rootThe function can easily obtain the root node. However, this function is not available in Oracle 9i.

We can indirectly obtain the root node through the following methods:

Select substr (. id_full_path, <br/> 2, <br/> decode (instr (. id_full_path, '^', 2), <br/> 0, <br/> length (id_full_path), <br/> instr (. id_full_path, '^', 2)-2) root_id, <br/>. * <br/> from (select T. *, sys_connect_by_path (T. bo_project_id, '^') id_full_path <br/> from bo_project T <br/> where biz_year = '000000' <br/> connect by T. bo_project_id = prior T. parent_project) A <br/>