media library treeview

[marvinklein]

i have a datset, which i store in xml. it has three tables, each with one column. "artists" "titles" "filepath"
i want to make artists unique, so if two files with the same artist are read from their id3 tag, then they both get pointed to the same item in the artist table, rather than having two artist items with the same value.
the point is that i can select an artist from the artists table and then i can easily see all the files with that artist.
how do i set up this kind of relation?