別名列SQL

Question

我有兩個簡單的列：datetime PayDate和int Amount 我試圖寫一個查詢，每天分開計數Amount但它不起作用。

SELECT YEAR(PayDate) + '/' + MONTH(PayDate) + '/' + DAY(PayDate) as a, 
COUNT(Amount) as b 
FROM TABLE1 
GROUP BY a,b 

謝謝你的幫忙。

Answer 1

你爲什麼這一切混亂的字符串連接困擾？如果您想要特定輸出，請在客戶端上格式化。儘可能使用基本類型而不是字符串。

SELECT CONVERT(DATE, PayDate) AS a, COUNT(Amount) AS b 
FROM dbo.TABLE1 
GROUP BY CONVERT(DATE, PayDate); 

如果你有合理複雜的表達式，以避免重複它是使用子查詢或CTE最簡單的方法：

SELECT a, COUNT(b) FROM 
(SELECT CONVERT(DATE, PayDate) AS a, Amount AS b FROM dbo.TABLE1) AS x 
GROUP BY a; 

-- or 

WITH x(a,b) AS 
(SELECT CONVERT(DATE, PayDate), Amount FROM dbo.TABLE1) 
SELECT a, COUNT(b) FROM x 
GROUP BY a; 

（我不知道你爲什麼被兩個分組a和b在你的問題中。）

Answer 2

至少在SQL Server中，不能在GROUP BY語句中使用別名。你必須重複說明。

傷心，但是的確如此。

SELECT YEAR(PayDate) + '/' + MONTH(PayDate) + '/' + DAY(PayDate) as a, 
COUNT(Amount) as b 
FROM TABLE1 
GROUP BY YEAR(PayDate) + '/' + MONTH(PayDate) + '/' + DAY(PayDate),COUNT(Amount) 

Answer 3

你不能在GROUP BY語句中使用別名。並且無需使用GROUP BY Count(Amount)

SELECT YEAR(PayDate) + '/' + MONTH(PayDate) + '/' + DAY(PayDate) as a, 
COUNT(Amount) as b 
FROM TABLE1 
GROUP BY YEAR(PayDate) + '/' + MONTH(PayDate) + '/' + DAY(PayDate) 

或者其他方式在SQL Server中做到這一點：

SELECT Convert(varchar(20),PayDate,111) as a, 
COUNT(Amount) as b 
FROM TABLE1 
GROUP BY Convert(varchar(20),PayDate,111) 

見Cast and Convert

Answer 4

在MySQL上，你也可以得到日期時間列的日期，只需購買使用。我不知道爲什麼你會在這種情況下通過別名b分組。在大多數情況下，您可能還想按日期值排序。

SELECT DATE(PayDate) as a, COUNT(Amount) as b 
FROM TABLE1 
GROUP BY a 
ORDER BY a