SQL組行基於列的值

Question

實例地址表

ID, EmployeeID, Address 

1, 100, TownA 
2, 200, TownA 
3, 300, TownB 

我怎麼能返回所有employess計數爲每一個獨特的地址？

e.g

EmployeeCount, Address 

2 TownA 
1, TownB 

Answer 1

你應該這樣做沿着此線的東西。

SELECT count(EmployeeID) as EmployeeCount, Address FROM table GROUP BY Address 

Answer 2

這是一個簡單的分組和count（列）

SELECT Count(*) EmployeeCount, Address 
FROM yourTable 
GROUP BY Address