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
[{'Template_Type_Description': 'Presentation'}, {'Template_Type_Description': 'Paper'}, {'Template_Type_Description': 'Book'}, {'Template_Type_Description': 'Advertisement'}]