Trial to Evaluate the Efficacy on Glycemic Variability and Safety of Gemigliptin Compared With Dapagliflozin Added on Metformin Alone or Diabetes Medication Naïve Patient in Type 2 Diabetes Mellitus (Stable II Study)

For patients who have been randomized to Gemigliptin(Experimental arm), the patients continue to take a gemigliptin 50mg 1 tablet by once daily during study treatment period(Visit 3(day 1)\~Visit 6(day 91))

For patients who have been randomized to Dapagliflozin(Active Comparator arm), the patients continue to take a dapagliflozin 10mg 1 tablet by once daily during study treatment period(Visit 3(day 1)\~Visit 6(day 91))

"doing exercise with about intermediate intensity(50\~70%) for ≥150minutes in total over at least 3 times(every other day) weekly should be recommended and regular diet without greater changes in life style as much as possible during the whole study period.~the questionnaire regarding diet/exercise will be collected at -day 6, day 1, day29, day85, day 91"

For patients who have been screening completely, the subjects will be attached CGMS(ipro-2) twice from Visit 2(-day 6) to Visit 3(day 1) and Visit 5(day 85) to Visit 6(day 91)

For patients who have been taking metformin, the patients who had taken at least 1000 mg of metformin daily and continue the same dosage and administration as before participant in the study