SELECT
*
FROM
POPU_TRANSITION as P
INNER JOIN
PREFECTURE as PP,
(SELECT PF_CODE, TOTAL_AMT FROM POPU_TRANSITION WHERE SURVEY_YEAR = 2015) as P2015,
(SELECT PF_CODE, TOTAL_AMT FROM POPU_TRANSITION WHERE SURVEY_YEAR = 2020) as P2020
ON
P.PF_CODE = PP.PF_CODE,
P.PF_CODE = P2015.PF_CODE