SQL 按列计数函数

Question

CusID   Order
3001    Hotdog
3001    Sausage
3002    Sausage
3003    Burger
3003    Hotdog
3002    Hotdog
3001    Burger

我将如何使用这个计数函数？

SELECT COUNT(CusID) AS NumOfOrders FROM Orders

期望的输出

CusID   NumOfOrders
3001    3
3002    2
3003    2

Answer 1

你需要一个 group by:

SELECT CusId, COUNT(CusID) AS NumOfOrders
FROM Orders
group by CusId
order by CusId;