sql - Create column that stores hierarchy as comma separated values -

i have table has 2 columns unit, m_unit shown below:

 +------+--------+ | unit | m_unit | +------+--------+ |   10 |     12 | |   15 |     19 | |   12 |     16 | |   13 |     15 | |   19 |     14 | |   14 |     11 | +------+--------+ 

i want create column h_tree stores hierarchy comma separated values after recursively searching through unit & m_unit such h_tree starts unit , ends last possible m_unit shown below:

 +------+--------+----------------+ | unit | m_unit |     h_tree     | +------+--------+----------------+ |   10 |     12 | 10,12,16       | |   15 |     19 | 15,19,14,11    | |   12 |     16 | 12,16          | |   13 |     15 | 13,15,19,14,11 | |   19 |     14 | 19,14,11       | |   14 |     11 | 14,11          | +------+--------+----------------+ 

apologies if not clear enough, let me know if confusing. thanks.

this should produce want:

with data (unit, m_unit) (     select 10, 12 dual union     select 15, 19 dual union     select 12, 16 dual union     select 13, 15 dual union     select 19, 14 dual union     select 14, 11 dual) select     unit,     m_unit,     unit || ',' || listagg(root_unit, ',') within group (order depth) h_tree (     select         id, unit, m_unit,         level depth, connect_by_root m_unit root_unit             (select rownum id, unit, m_unit data) data     connect         prior unit = m_unit) group     id,     unit,     m_unit 

if lines in table distinct id column not necessary.