Question

我正在尝试将MySQL数据库转换为MSSQL数据库，但我在翻译查询时正在尝试一些问题，特别是以下内容：

的MySQL

SELECT GROUP_CONCAT( parent.Name
ORDER BY parent.Lft
SEPARATOR  "«" ) AS Path, node.Description
FROM  `DB`.`Categories` AS node,  `DB`.`Categories` AS parent
WHERE node.Lft BETWEEN parent.Lft AND parent.Rgt AND node.ID = 2
GROUP BY node.Name, node.ID
ORDER BY node.Lft LIMIT 1;

我得到的结果就是这个，这是我想要获得的结果：

+-------------------------------+
| Path                          |
+-------------------------------+
| Master Node « Vehicles « Cars |
+-------------------------------+

MS SQL

我尝试使用帖子https://stackoverflow.com/a/5981860/2098159

中的建议重新创建MySQL查询

SELECT STUFF((SELECT  ' « ' + [Name] FROM [DB].[dbo].[Categories] FOR XML PATH ('')), 1, 1, '') AS [Path] 
FROM [DB].[dbo].[Categories] AS node, [DB].[dbo].[Categories] AS parent 
WHERE node.[Lft] BETWEEN parent.[Lft] AND parent.[Rgt] AND node.[ID] = 7 
GROUP BY node.[Name], node.[ID], node.[Lft] ORDER BY node.[Lft];

我得到的结果就是这个，无论我选择哪个ID：

+---------------------------------------------+
| Path                                        |
+---------------------------------------------+
| « Master Node « Vehicles « Cars « Computers |
+---------------------------------------------+

此时我只创建一个包含4条记录的表：主节点，车辆，汽车和计算机;只是为了测试。

我不知道我错过了什么。有没有人有建议？

提前致谢。

Answer 1

问题是您缺少xml路径部分中的条件：

SELECT 
  STUFF((
    SELECT  ' « ' + [Name] 
    FROM [DB].[dbo].[Categories] C 
    WHERE C.ID = node.ID -- a criteria here is needed to get correct rows
  FOR XML PATH ('')), 1, 1, '') AS [Path] 
FROM 
  [DB].[dbo].[Categories] AS node, 
  [DB].[dbo].[Categories] AS parent 
WHERE 
  node.[Lft] BETWEEN parent.[Lft] AND parent.[Rgt] AND 
  node.[ID] = 7 
GROUP BY 
  node.[Name], 
  node.[ID], 
  node.[Lft] 
ORDER BY 
  node.[Lft];

我的假设是ID足以识别正确的行。

Answer 2

这里我放置了正确的查询。

SELECT STUFF((SELECT CAST(' « ' AS varchar(MAX)) + parent.name
  FROM Categories AS node, Categories AS parent
 WHERE node.[Lft] BETWEEN parent.[Lft] AND parent.[Rgt]
   AND node.[ID] = 7
 ORDER BY node.lft
   FOR XML PATH('')), 1, 1, '') as Path

我唯一无法删除的是第一个'«'

+---------------------------------+
| Path                            |
+---------------------------------+
| « Master Node « Vehicles « Cars |
+---------------------------------+

如何使用GROUP_CONCAT将MySQL查询正确转换为MSSQL查询

2 个答案: