Question

我尝试针对World Database的城市表编写查询，该表同时计算每个国家/地区的重复城市数量以及重复值。这部分是有效的，但我也希望显示每个国家的重复城市总数。

到目前为止，这是我的SQL（仅限于一个用于测试的国家/地区）：

Select c1.country_code, c1.city, citc.city_duplicates 
from cities c1 
join 
 (SELECT c2.id, c2.country_code, c2.city, COUNT(c2.city) AS `city_duplicates`  
    FROM cities c2
    WHERE c2.country_code = 'om'
    GROUP BY country_code, region_code, latitude, longitude, city 
    HAVING city_duplicates > 1
    ORDER BY country_code) citc
 on c1.id = citc.id;

以下是结果：

# country_code, city, city_duplicates
'om',           'zi', '2'
'om',           'zi', '2'

我希望看到另一栏中写着＆＃39; 4＆＃39;为国家总数。

如果你可以用desc顺序的重复数排序，那么可以获得奖励积分。

以下是一些示例数据：

# country_code, city, accent_city, region_code, population, latitude, longitude, id
'om', 'abailah', 'Abailah', '02', '0', '24.266666', '56.150002', '2050634'
'om', 'a`bal', 'A`bal', '05', '0', '24.433332', '56.049999', '2050635'
'om', '`abat', '`Abat', '04', '0', '22.550556', '59.328056', '2050636'
'om', '`abayah', '`Abayah', '06', '0', '23.175278', '58.814167', '2050637'
'om', '`abbasah', '`Abbasah', '02', '0', '23.916668', '57.216667', '2050638'
'om', '`ablah', '`Ablah', '05', '0', '23.168333', '56.909168', '2050639'
'om', 'abu `abali', 'Abu `Abali', '02', '0', '23.771111', '57.676945', '2050640'
'om', 'abu akaisha', 'Abu Akaisha', '04', '0', '21.400000', '59.283333', '2050641' 
om  zi  Z̧ahir  00  0   19.100000   56.966667   2053410
om  zi  Z̧abyah 02  0   24.350000   56.366669   2053408
ad  aixirivall  Aixirivall  06  0   42.466667   1.500000    3
ad  aixirvall   Aixirvall   06  0   42.466667   1.500000    4
ad  aixovall    Aixovall    06  0   42.466667   1.483333    5
ad  andorra Andorra 07  0   42.500000   1.516667    6

以下是国家/地区的结果：

# country_code, city, city_duplicates, country_duplicates
'om',           'zi', '2',             '4'
'om',           'zi', '2',             '4'

谢谢！

Answer 1

如果要在另一列中显示总和，您几乎必须总结外部查询中的city_duplicates字段并将其连接到子查询的结果：

SELECT c2.country_code, c2.city, COUNT(c2.city) AS `city_duplicates`, t2.country_duplicates
    FROM cities c2
    INNER JOIN (SELECT t.country_code, SUM(t.city_duplicates) as country_duplicates
                FROM (SELECT c3.country_code, c3.city, COUNT(c3.city) AS `city_duplicates`  
                      FROM cities c3
                      WHERE c3.country_code = 'om'
                      GROUP BY country_code, region_code, latitude, longitude, city 
                      HAVING city_duplicates > 1) t
                 GROUP BY t.country_code) t2 ON c2.country_code=t2.country_code
    WHERE c2.country_code = 'om'
    GROUP BY c2.country_code, region_code, latitude, longitude, city 
    HAVING city_duplicates > 1
    ORDER BY country_duplicates, c2.country_code

但是，如果您希望将摘要放在单独的记录中，那么代码会简单得多，因为您可以使用MySQL的rollup group by`修饰符。

Answer 2

只需计算您的城市重复次数

 Select c1.country_code, c1.city, citc.city_duplicates ,sum(citc.city_duplicates) as country_duplicate 
from cities c1 
join 
 (SELECT c2.id, c2.country_code, c2.city, COUNT(c2.city) AS `city_duplicates`  
FROM cities c2
WHERE c2.country_code = 'om'
GROUP BY country_code, region_code, latitude, longitude, city 
HAVING city_duplicates > 1
ORDER BY country_code) citc
 on c1.id = citc.id group by c1.country_code order by c1.country_code desc;

MySQL计算每个国家/地区的重复城市

2 个答案: