如何在MySQL SELECT結果集中包含自定義計數？

Question

我有以下兩個表：

TABLE: area 
*City_ID *Number Name 
-------- ------- ---- 
SUR  1   Fleetwood 
SUR  2   Whalley 
SUR  3   Guildford 
SUR  4   Newton 
SUR  5   Cloverdale 
SUR  6   South Surrey 
ABB  1   Abbotsford East 
ABB  2   Abbotsford West 
ABB  3   Aberdeen 
ABB  4   Bradner 
ABB  5   Central Abbotsford 
ABB  6   Matsqui 
ABB  7   Poplar 
ABB  8   Sumas Mountain 
ABB  9   Sumas Prairie 

TABLE: city 
*ID  Name 
---  ---- 
SUR  Surrey 
ABB  Abbotsford 
LAN  Langley 

使用下面的語句：

SELECT DISTINCT area.City_ID, city.Name 
FROM area 
INNER JOIN city 
WHERE area.City_ID = city.ID 

我得到：

SELECT: 
City_ID city.Name 
------- --------- 
SUR  Surrey 
ABB  Abbotsford 

但是我怎麼選擇以下內容：

SELECT: 
City_ID city.Name area_COUNT 
------- --------- ---------- 
SUR  Surrey  6 
ABB  Abbotsford 9 

其中area_COUNT是area中每行對應的行數City_ID？

Answer 1

使用GROUP BY而不是DISTINCT：

SELECT city.City_ID, city.Name, COUNT(*) 
FROM area 
INNER JOIN city 
WHERE area.City_ID = city.ID 
GROUP BY city.ID 

Answer 2

附加在其結尾

SELECT area.City_ID, city.Name, count(*) as area_COUNT 
FROM area 
INNER JOIN city 
WHERE area.City_ID = city.ID 
GROUP BY area.City_ID 

Answer 3

你也應該在GROUP BY子句中添加名稱

SELECT area.City_ID, city.Name, count(*) as area_COUNT 
FROM area 
INNER JOIN city 
WHERE area.City_ID = city.ID 
GROUP BY area.City_ID,City.Name 

Answer 4

使用GROUP BY代替組DISTINCT：

SELECT city.City_ID，city.Name，COUNT（*）FROM 面積 INNER JOIN城市 WHERE area.City_ID = city.ID GROUP BY city.ID