SQL查詢，每月用戶數（日期時間）

Question

我有我想更改爲以下格式的SQL表：

我已經有一個表，但我不能使其從另一個表中統計用戶並將其插入到列中。

Answer 1

我建議你，而不是表使用視圖這樣的：

CREATE VIEW vw_CountUsersPerMonth 
AS 

SELECT YEAR(SignUpTime) as [Year], 
     DATENAME(month,SignUpTime) AS [MonthName], 
     COUNT(UserID) AS [CountUsers] 
FROM Tbl_Users 
GROUP BY YEAR(SignUpTime), DATENAME(month,SignUpTime)) 

Answer 2

這應該做到這一點，如果你正在使用tSQL，但不同年份的相同月份呢？

;WITH CTE AS (
SELECT DATENAME(month,SignUpTime) AS [MonthName], 
     COUNT(UserID) AS [CountUsers] 
FROM Tbl_Users 
GROUP BY DATENAME(month,SignUpTime)) 

UPDATE A 
SET A.[CountUsers]=B.[CountUsers] 
FROM Tbl_CountUsersPerMonth AS A LEFT OUTER JOIN 
    CTE AS B ON A.[MonthName]=B.[MonthName]