mysql讓count為0的記錄也顯示出來

在mysql 下執行如下命令：

select use_city,count(*) from data where os="Windows 2003 Std" group by use_city;

得到的結果為：

+-----------+----------+
| use_city | count(*) |
+-----------+----------+
| Beijing | 2 |
| Chengdu | 2 |
| Chongqing | 1 |
| Dalian | 2 |
| Fuzhou | 2 |
| Guangzhou | 2 |
| Hangzhou | 2 |
| Nanjing | 2 |
| Shanghai | 21 |
| Shenyang | 5 |
| Wuhan | 1 |
+-----------+----------+
11 rows in set (0.01 sec)

共有11條記錄，問題是其中有一個城市“Tianjing”是沒有記錄符合的，怎么讓他顯示成

+-----------+----------+
| use_city | count(*) |
+-----------+----------+
| Beijing | 2 |
| Chengdu | 2 |
| Chongqing | 1 |
| Dalian | 2 |
| Fuzhou | 2 |
| Guangzhou | 2 |
| Hangzhou | 2 |
| Nanjing | 2 |
| Shanghai | 21 |
| Tianjing | 0 |
| Shenyang | 5 |
| Wuhan | 1 |
+-----------+----------+

讓它count為0的記錄也顯示出來，做法如下：

 

SELECT
use_city,
COUNT(CASE WHEN os='Windows 2003 Std' THEN 1 ELSE NULL END)
FROM
data
GROUP BY
use_city