SQL Server查詢XML數據類型性能問題

Question

我有一個XML文件存儲在我的表records的XML數據類型列data中。

表看起來是這樣的：

create table records 
(
    id int, 
    type nvarchar(28), 
    data xml, 
    posted datetime 
) 

XML數據：

<Properties> 
    <data> 
     <Name>novel</Name> 
     <Gender>Female</Gender> 
     <Age>32</Age> 
     <Salary>55k</Salary> 
     <Phone>123-123</Phone> 
    </data> 
</Properties> 

我目前使用下面的查詢，提取從XML列，其花費的時間比多分鐘在20K記錄數據

。

select 
    id, 
    posteddate, 
    CONVERT(NVARCHAR(500), data.query('data(Properties/data/Name)')) AS Name, 
    CONVERT(NVARCHAR(500), data.query('data(Properties/data/Gender)')) AS Gender, 
    CONVERT(NVARCHAR(500), data.query('data(Properties/data/Age)')) AS Age, 
    CONVERT(NVARCHAR(500), data.query('data(Properties/data/Salary)')) AS Salary, 
    CONVERT(NVARCHAR(500), data.query('data(Properties/data/Phone)')) AS Phone 
from 
    records 
where 
    type = 'personnel_xml' 

我很新來SQL Server中的XML提取。我想我沒有遵循標準優化方法來提取XML元素。

那麼，任何人都可以幫助我如何優化這種情況，因爲我需要從我的xml中提取100個這樣的元素存儲爲列。

Answer 1

假設您在xml中有多個<data>。注意我添加了一個擴展的xml文件，它將有兩組。

Declare @table table (id int,data xml) 
Insert Into @table values (1,'<Properties><data><Name>novel</Name><Gender>Female</Gender><Age>32</Age><Salary>55k</Salary><Phone>123-123</Phone></data> 
<data><Name>Another Name</Name><Gender>Male</Gender><Age>45</Age><Salary>75k</Salary><Phone>555-1212</Phone></data> 
</Properties>') 

;with cte as (
     Select ID 
      ,RN = Row_Number() over (Partition By ID Order By (Select Null)) 
      ,Data = m.query('.') 
     From @table AS t 
     Cross Apply t.Data.nodes('/Properties/data') AS A(m) 
) 
Select ID 
     ,RN 
     ,Name = Data.value('(data/Name)[1]' ,'nvarchar(500)') 
     ,Gender = Data.value('(data/Gender)[1]','nvarchar(500)') 
     ,Age = Data.value('(data/Age)[1]' ,'nvarchar(500)') 
     ,Salary = Data.value('(data/Salary)[1]','nvarchar(500)') 
     ,Phone = Data.value('(data/Phone)[1]' ,'nvarchar(500)') 
From cte 

返回

ID RN Name   Gender Age  Salary Phone 
1 1 novel   Female 32  55k  123-123 
1 2 Another Name Male 45  75k  555-1212 

Answer 2

爲了得到一個值了XML的SQL Server中，你應該使用value() Method (xml Data Type)。對於無類型的XML，您應該指定text()節點以獲得更好的性能。

select R.id, 
     R.posted, 
     R.data.value('(/Properties/data/Name/text())[1]', 'nvarchar(500)') as Name, 
     R.data.value('(/Properties/data/Gender/text())[1]', 'nvarchar(10)') as Gender, 
     R.data.value('(/Properties/data/Age/text())[1]', 'int') as Age, 
     R.data.value('(/Properties/data/Salary/text())[1]', 'nvarchar(10)') as Salary, 
     R.data.value('(/Properties/data/Phone/text())[1]', 'nvarchar(30)') as Phone 
from dbo.records as R 
where type = N'personnel_xml';