SELECT DISTINCT T1.template_type_description FROM Ref_template_types AS T1 JOIN Templates AS T2 ON T1.template_type_code  = T2.template_type_code JOIN Documents AS T3 ON T2.Template_ID  =  T3.template_ID
What are the distinct template type descriptions for the templates ever used by any document?
SELECT DISTINCT T1.template_type_description FROM Ref_template_types AS T1 JOIN Templates AS T2 ON T1.template_type_code = T2.template_type_code JOIN Documents AS T3 ON T2.Template_ID = T3.template_ID
select distinct t1 . template_type_description from ref_template_types as t1 join templates as t2 on t1 . template_type_code = t2 . template_type_code join documents as t3 on t2 . template_id = t3 . template_id
What are the distinct template type descriptions for the templates ever used by any document ?