SQL “tree-like” query - most parent group

Question

I\'m having some trouble doing a \"tree-like\" query (what do we call this?) in SQL.

Take a look at my diagram below (table and column names are in danish - sorry ab

Answer 1

I came up with a solution that solves the problem of listing ALL the groups for each customer. Parent and child groups.

What do you think?

WITH GroupTree
AS
(
    SELECT kg.KundeId, g.Id GruppeId
    FROM ActiveDirectory.Gruppe g
    INNER JOIN ActiveDirectory.Kunde_Gruppe kg ON g.Id = kg.GruppeId
    AND (EXISTS (SELECT * FROM ActiveDirectory.Gruppe_Gruppe WHERE ParentGruppeId = g.Id)
    OR NOT EXISTS (SELECT * FROM ActiveDirectory.Gruppe_Gruppe WHERE ParentGruppeId = g.Id))

    UNION ALL

    SELECT GroupTree.KundeId, gg.ChildGruppeId
    FROM ActiveDirectory.Gruppe_Gruppe gg
    INNER JOIN GroupTree ON gg.ParentGruppeId = GroupTree.GruppeId
)
SELECT KundeId, GruppeId
FROM GroupTree

OPTION (MAXRECURSION 32767)