Hi Geert,
Many thanks for your answer.
Indeed my wording was not correct, the ID I retreived is the one of the Goup I'm searching for.
I did some tries and finally got the right query, here it is:
select * from t_object
where Stereotype = 'myStereotype' <= used to narrow the search
and ea_guid in
(select EntityID from t_seclocks
where GroupID = '{5CD33F3E-022C-4ccc-85BE-557AB3F9BA74}' <= GUID of the Group
and EntityType = 'Element')
Michel