traversing a tree in two different columns in sqlite using python -

my sqlite database has 2 columns named child , parent , element value 0 root of tree , sample data:

child  parent 33     16 16     0 45     39 30     0 

i trying write sqlite query determine number of trees & path shown below number of trees : 2

0 16 33 0 30 49 

i able find out rows 0s ...but not able think of logic generate path..

any suggestions please

how many children can have parent? in example, seem assume each 'root' parent has 1 child. maybe start like:

select a.parent, a.child, b.child mytable join mytable b   on a.child = b.parent a.parent = 0; 

(not tried). should more precise in question.

if interested number of trees, maybe like:

select count(*) mytable parent = 0; 

best regards.