oracle - Connect by clause to get the top of hierarchy -

i facing issue while using connect by clause in oracle finding hierarchical data. let me give example: parent part has child part b , b has child part c. when using connect by clause able 3 levels want top level, i.e. a.

oracle has level pseudocolumn can use:

select   mytable.id,   mytable.parentid mytable level = 1 connect prior mytable.id = mytable.parentid 

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to find top-level (root) value level, precede column name connect_by_root operator:

select   mytable.id,   mytable.parentid,   connect_by_root mytable.id "top level id" mytable connect prior mytable.id = mytable.parentid