SQL查询使用列ALIAS

Question

这应该很容易，但我得到一个“无效列名称”错误。

SELECT Transaction, COUNT(ItemId) AS ItemCount 
FROM TransactionTable 
WHERE ItemCount > 5 
GROUP BY Transaction 
ORDER BY ItemCount DESC 

这种说法作品，未经这似乎是双重标准，对我来说，因为ORDER BY使用列别名WHERE子句。

Answer 1

使用HAVING，并指定统计再次

SELECT Transaction, COUNT(ItemId) AS ItemCount 
FROM TransactionTable 
GROUP BY Transaction 
HAVING COUNT(ItemId) > 5 
ORDER BY ItemCount DESC 

原因ORDER BY正在与别名是因为SQL查询顺序

处理FROM（包括联接）
ON
OUTER
其中
GROUP BY
HAVING
SELECT
ORDER BY
TOP

Answer 2

SELECT [Transaction], COUNT(ItemId) AS ItemCount 
FROM TransactionTable 
WHERE ItemCount > 5 
GROUP BY COUNT(ItemId) 
ORDER BY COUNT(ItemId) DESC 

Answer 3

您可以参考列别名在ORDER BY如（逻辑）这是SELECT后处理。要使用WHERE或HAVING子句中的列别名，您可以在表格表达式中定义SELECT，例如，如下。

;WITH cte 
    AS (SELECT Transaction , 
       COUNT(itemid) AS itemcount 
     FROM transactiontable 
     GROUP BY Transaction) 
SELECT Transaction , 
     itemcount 
FROM transactiontable 
WHERE itemcount > 5 
ORDER BY itemcount DESC 

Answer 4

WITH tempTable AS 
(
    SELECT Transaction, COUNT(ItemId) AS ItemCount 
    FROM TransactionTable 
) 
SELECT * 
FROM tempTable 
WHERE ItemCount > 5 
GROUP BY Transaction 
ORDER BY ItemCount DESC