CREATE TABLE Ref_Service_Types (Service_Type_Description VARCHAR2, Service_Type_Code VARCHAR2)
CREATE TABLE Services (Service_Type_Code VARCHAR2)

What is the description and code of the type of service that is performed the most often?
SELECT T1.Service_Type_Description, T1.Service_Type_Code FROM Ref_Service_Types AS T1 JOIN Services AS T2 ON T1.Service_Type_Code = T2.Service_Type_Code GROUP BY T1.Service_Type_Code ORDER BY COUNT(*) DESC LIMIT 1
SELECT "T1"."Service_Type_Description", "T1"."Service_Type_Code" FROM "Ref_Service_Types" "T1" JOIN "Services" "T2" ON "T1"."Service_Type_Code" = "T2"."Service_Type_Code" GROUP BY "T1"."Service_Type_Code" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY