SELECT
    PORT.PORT_CODE AS 港コード,
    PORT.PORT_NAME AS 港名,
    IMM110.AMT AS 入国者数,
    IMM120.AMT AS 出国者数,
    IMM110.AMT - IMM120.AMT AS 差分
FROM 
    IMMIGRATION AS IMM110 
    JOIN IMMIGRATION AS IMM120
    ON IMM110.PORT_CODE = IMM120.PORT_CODE
    AND IMM110.KIND_CODE = 110
    AND IMM110.GROUP_CODE = 120
    AND IMM120.KIND_CODE = 120
    AND IMM120.GROUP_CODE = 120
    JOIN PORT ON IMM110.PORT_CODE = PORT.PORT_CODE
WHERE IMM110.AMT > IMM120.AMT
ORDER BY
    差分 DESC, 港コード;