MySQL多列，單個查詢

Question

我有一個數據庫，裏面存有客戶的數據。我需要知道我們在個別城市和國家有多少客戶。我必須用單個查詢來完成。

我的表是客戶，我有列城市和國家（都是varchar），其中包含有關它的信息。

所需的查詢的輸出應該是這樣的：

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

感謝

Answer 1

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

編輯顯示示例表和查詢的輸出：

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)