SQL DENSE_RANK和PARTITION BY

Question

我不完全了解以下列出的查询结果：

CREATE TABLE #tmpAccountsTable (ID INT PRIMARY KEY, AccountID INT, 

AccountName varchar(20), CompanyID int, CompanyName varchar(50))
INSERT INTO #tmpAccountsTable (ID, AccountID, AccountName, CompanyID, CompanyName)
SELECT 1 AS ID, 1 AS AccountID, 'ABC Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 2 AS ID, 1 AS AccountID, 'ABC Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 3 AS ID, 2 AS AccountID, 'DEF Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 4 AS ID, 3 AS AccountID, 'GHI Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 5 AS ID, 4 AS AccountID, 'JKL Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 6 AS ID, 1 AS AccountID, 'ABC Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 7 AS ID, 1 AS AccountID, 'ABC Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 8 AS ID, 1 AS AccountID, 'ABC Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName UNION
SELECT 9 AS ID, 2 AS AccountID, 'DEF Account' AS AccountName, 1 AS CompanyID, 'Stark Enterprise' AS CompanyName

SELECT DENSE_RANK() OVER (PARTITION BY AccountID ORDER BY CompanyName) as AccountRANK, * FROM #tmpAccountsTable

DROP TABLE #tmpAccountsTable

执行上述操作，我得到以下结果集：

根据我对SELECT DENSE_RANK() OVER (PARTITION BY AccountID ORDER BY CompanyName) as AccountRANK, * FROM #tmpAccountsTable的理解，应该为所有相同的AccountId创建一个分区，并且它们应该收到相同的DENSE_RANK()值，但是可以看出，这是并非如此。

我想念什么？

Answer 1

如果您想为每个AccountId分配一个单独的值，则该值应该是ORDER BY而不是PARTITION BY的一部分：

SELECT DENSE_RANK() OVER (ORDER BY AccountID, CompanyName) as AccountRANK, *
FROM #tmpAccountsTable;

PARTITION BY用于重置计数器，因此每个AccountId从1开始。然后对CompanyNames进行排序。因为它们都具有相同的值，所以结果为1。