MySQL 多列、单查询

Question

我有一个数据库，里面保存着客户的数据。我需要知道我们在各个城市和国家有多少客户。我必须用单个查询来完成它。

我的表是客户，我有城市和国家列(均为varchar)，其中包含有关它的信息。

所需的查询输出应如下所示:

City | NumberOfCustomers | Country | NumberOfCustomers |
--------------------------------------------------------

谢谢

Answer 1

select city, country, count(*) from tbl group by 1,2 with rollup

编辑以显示示例表和该查询的输出:

mysql> select * from location;
+-------+---------+
| city  | country |
+-------+---------+
| City1 | US      |
| City2 | US      |
| City2 | US      |
| City3 | CA      |
| City3 | CA      |
| City3 | JP      |
+-------+---------+
6 rows in set (0.00 sec)

mysql> select city, country, count(*) from location group by 1,2 with rollup;
+-------+---------+----------+
| city  | country | count(*) |
+-------+---------+----------+
| City1 | US      |        1 |
| City1 | NULL    |        1 |
| City2 | US      |        2 |
| City2 | NULL    |        2 |
| City3 | CA      |        2 |
| City3 | JP      |        1 |
| City3 | NULL    |        3 |
| NULL  | NULL    |        6 |
+-------+---------+----------+
8 rows in set (0.01 sec)