请问数据库五张表如何关联查询？

Question

五张表如下：

cdn_duty表（a）

cdn_duty2city表(b)

cdn_duty2province表(c)

city_data表(d)

province_data表(e)

下面是我写的一部分查询：

问题是我不明白如何将c表关联进去实现这个效果：

小白求大神指教！！多谢！！！

Answer 1

琢磨了三天终于实现了下面是完整查询语句，（可能不是最好的，欢迎大神指教！）

SELECT
    aa.sno,
    aa.duty_name,
    aa.duty_mail,
    aa.city_name,
    concat(
        IFNULL(aa.province_name, ''),
        IFNULL(bb.province_name, '')
    ) AS province_name
FROM
    (
        SELECT
            a.sno,
            a.duty_name,
            a.duty_mail,
            d.city_name,
            e.province_name
        FROM
            qiyq.cdn_duty AS a
        LEFT JOIN qiyq.cdn_duty2city AS b ON a.sno = b.sno_duty
        LEFT JOIN qiyq2.city_data AS d ON b.sno_city = d.sno
        LEFT JOIN qiyq2.province_data AS e ON d.sno_province = e.sno
    ) aa
LEFT JOIN (
    SELECT
        a.sno,
        a.duty_name,
        a.duty_mail,
        e.province_name
    FROM
        qiyq.cdn_duty AS a
    LEFT JOIN qiyq.cdn_duty2province AS c ON a.sno = c.sno_duty
    LEFT JOIN qiyq2.province_data AS e ON c.sno_province = e.sno
) bb ON aa.sno = bb.sno
ORDER BY
    aa.sno

其中concat参考自：https://zhidao.baidu.com/question/547611101.html

效果如下：