How build tree use two table from database


I have one question.
Is possible to build a tree using data from two tables?

If I work with one table tasks all work fine. But with two tables not work.

I have two tables ( group and objective ).
In table group I have fields (id, name).
In table objective I have fields (id, groupId, objectiveId, objectiveName).

I must create tree where:
+English group (from group table)
Reading English (from objective table)
Writing English (from objective table)
English litterature (from objective table)
+Math methods (from group table)
Algebra (from objective table)
Geometry (from objective table)

I try use this code but it not work

Thank you very much,

connector package contains sample
which implements exactly the same what you like.
This connector package is available here: …