SQL Group By 和对两列进行计数

Question

我有一个 MySQL 表，数据如下：-

country | city
---------------
italy   | milan
italy   | rome
italy   | rome
ireland | cork
uk      | london
ireland | cork

我想查询这个并按国家和城市分组，并计算城市和国家的计数，如下所示：-

country | city   | city_count | country_count
---------------------------------------------
ireland | cork   |          2 |             2
italy   | milan  |          1 |             3
italy   | rome   |          2 |             3
uk      | london |          1 |             1

我可以：-

SELECT country, city, count(city) as city_count
FROM jobs
GROUP BY country, city

这给了我：-

country | city   | city_count 
-----------------------------
ireland | cork   |          2 
italy   | milan  |          1 
italy   | rome   |          2
uk      | london |          1

有没有获取country_count 的指针？

Answer 1

您可以使用相关子查询：

SELECT country, city, count(city) as city_count,
       (SELECT count(*)
        FROM jobs AS j2
        WHERE j1.country = j2.country) AS country_count
FROM jobs AS j1
GROUP BY country, city

演示在这里