Table schema:
CREATE TABLE Ref_Service_Types (Service_Type_Description VARCHAR, Service_Type_Code VARCHAR); CREATE TABLE Services (Service_Type_Code VARCHAR, Product_Name VARCHAR)

Question: What is the description of the service type which offers both the photo product and the film product?
SQL: SELECT T1.Service_Type_Description FROM Ref_Service_Types AS T1 JOIN Services AS T2 ON T1.Service_Type_Code = T2.Service_Type_Code WHERE T2.Product_Name = 'photo' INTERSECT SELECT T1.Service_Type_Description FROM Ref_Service_Types AS T1 JOIN Services AS T2 ON T1.Service_Type_Code = T2.Service_Type_Code WHERE T2.Product_Name = 'film'