從城市獲得客戶的百分比

Question

我想檢索居住在某些城市的注冊客戶的百分比。

目前我有這個

SELECT
COUNT(city) / Count(CustID) * 100 AS percent, city
FROM customer
GROUP BY City

當前，它為每一行提供100％的結果。
我在這里缺少明顯的東西。 如何解決查詢？

Answer 1

您需要在單獨的子查詢中獲得客戶總數：

SELECT COUNT(city) / (SELECT Count(CustID) FROM Customer) * 100 AS percent, city
FROM customer
GROUP BY City

或者，使用CROSS JOIN ：

SELECT
COUNT(city) / x.cnt * 100 AS percent, city
FROM customer
CROSS JOIN (SELECT Count(CustID) AS cnt FROM Customer) AS x
GROUP BY City

Answer 2

嘗試這個

SELECT
COUNT(city) / (SELECT Count(CustID) FROM Customer) * 100 AS percent, city
FROM customer c
GROUP BY City