SELECT
    tbl3.PORT_CODE AS 港コード
    ,tbl3.PORT_NAME AS 港名
    ,SUM(CASE WHEN tbl1.KIND_CODE = '110' THEN tbl1.AMT ELSE 0 END) AS 入国者数
    ,SUM(CASE WHEN tbl1.KIND_CODE = '120' THEN tbl1.AMT ELSE 0 END) AS 出国者数
    ,SUM(CASE WHEN tbl1.KIND_CODE = '110' THEN tbl1.AMT ELSE 0 END) - SUM(CASE WHEN tbl1.KIND_CODE = '120' THEN tbl1.AMT ELSE 0 END) AS 差分
FROM
    IMMIGRATION tbl1
INNER JOIN
    GRP tbl2
ON
    tbl1.GROUP_CODE = tbl2.GROUP_CODE
    AND tbl2.GROUP_CODE = '120'
INNER JOIN
    PORT tbl3
ON
    tbl1.PORT_CODE = tbl3.PORT_CODE
GROUP BY
    港コード
HAVING 
    差分 > 0
ORDER BY
    差分 DESC
    ,港コード DESC