问题描述
我的 XML 结构:
<Items> <Item> <guid>FC550573-7171-997F-752D-8D65590CBFD6</guid> <Objects> <Object> <type>0</type> <guid>E10D9DA9-2C8D-8024-2F07-DF21395811BF</guid> </Object> <Object> <type>0</type> <guid>D8338400-35C7-781E-A039-C0FDDF80714A</guid> </Object> </Objects> </Item> </Items>
填充对象表时:
CREATE TABLE [dbo].[Objects]( [item_guid] [varchar](36) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [type] [int] NOT NULL, [guid] [varchar](36) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ) ON [PRIMARY]
使用查询:
INSERT INTO [dbname].[dbo].[Objects] ([item_guid] ,[type] ,[guid]) SELECT X.source.query('../../guid').value('.','VARCHAR(36)') as item_guid, X.source.query('type').value('.','INT') as type, X.source.query('guid').value('.','VARCHAR(36)') as guid FROM( Select xmldata from XmlFiles where fullpath=@fp ) AS T(x) CROSS APPLY x.nodes('Items/Item/Objects/Object') As X(source)
这一行使查询变得非常慢:
This line is making the query VERY slow:
X.source.query('../../guid').value('.','VARCHAR(36)') as item_guid
这里的正确方法是什么?
What is the proper approach here?
推荐答案
使用 /text() 获取值有利于非类型化 XML 的性能.使用父轴 ../.. 也可能不好(如@marc_s 建议的那样).
Using /text() to get the value is good for performance on untyped XML. It can also be bad to use the parent axis ../.. (as @marc_s suggested).
这是一个带有额外交叉应用和 /text() 来获取值的版本.??
Here is a version with a extra cross apply and /text() to get the values.
试试这个:
select T2.N.value('(guid/text())[1]', 'uniqueidentifier') as item_guid, T3.N.value('(type/text())[1]', 'int') as type, T3.N.value('(guid/text())[1]', 'uniqueidentifier') as guid from (SELECT xmldata FROM dbo.XmlFiles WHERE fullpath = @fp) as T1(N) cross apply T1.N.nodes('Items/Item') as T2(N) cross apply T2.N.nodes('Objects/Object') as T3(N)
您必须判断哪个查询对您来说最快.
You have to be the judge which query is the fastest for you.