a table is structured like a linked list:

create ATable (
id integer not null,
fm_id integer not null
)

ID is unique for every row.

Every row (say row with ID 56) can have N children.

If N is 3, we could have tuples like

(100,56), (121,56), (133,56)

where all the 3 rows have different IDs, but all share the common
ancestor ID.

Given row with ID X, which SQL instruction(s) can list - say - 30
ancestors ?

Thank you

Duilio Foschi