Hierarchical/tree database for directories path in filesystem

Question

I want to store the directories (present on the disk) into a database, maintaining their hierarchical/tree structure.

Here\'s a figure:

Answer 1

You represent hierarchical data as a series of nodes each of which has an ID and a Parent ID. You could store your in a table called DIRTAB with 2 ID columns and one for the text of the individual directory name:

ID -- as a primary key  
PARENT_ID -- refers to the ID of the parent row in DIRTAB  
DIRNAME -- the text of the name eg Dir5  

SQLite lacks the CONNECT BY clause that Oracle has to process hierarchical data but I think if you're prepared to accept some ugly SQL you can approximate something hierarchical:

SELECT (CASE WHEN p5.DIRNAME IS NOT NULL THEN p5.DIRNAME || '/' ELSE '' END) ||
       (CASE WHEN p4.DIRNAME IS NOT NULL THEN p4.DIRNAME || '/' ELSE '' END) ||
       (CASE WHEN p3.DIRNAME IS NOT NULL THEN p3.DIRNAME || '/' ELSE '' END) ||
       (CASE WHEN p2.DIRNAME IS NOT NULL THEN p2.DIRNAME || '/' ELSE '' END) ||
       (CASE WHEN p1.DIRNAME IS NOT NULL THEN p1.DIRNAME || '/' ELSE '' END) ||
       p0.DIRNAME as FULLPATH
FROM DIRTAB p0
     LEFT OUTER JOIN DIRTAB p1 ON p1.ID = p0.PARENT_ID
     LEFT OUTER JOIN DIRTAB p2 ON p2.ID = p1.PARENT_ID
     LEFT OUTER JOIN DIRTAB p3 ON p3.ID = p2.PARENT_ID
     LEFT OUTER JOIN DIRTAB p4 ON p4.ID = p3.PARENT_ID
     LEFT OUTER JOIN DIRTAB p5 ON p5.ID = p4.PARENT_ID
WHERE p0.DIRNAME = 'Dir6'  

The trouble here is that you have to anticipate the maximum depth of you directory structure and expand the SQL statement to cope. I have done 6 levels as an example.
Also I'm assuming that SQLite has no problem concatenating empty strings. (Some DBs treat them as null and convert the whole expression result to null)