Question

我有一个包含xml数据的表。由于某些原因，xml值中的某些字段具有不一致的数据。我需要相应地修改它。在下面的模板中我们可以看到字段txtCapacity，该值超出范围值。我需要将其转换为正确的格式使其成为浮点数？

Below is the table structure

Table XML_Capacity 
( RID int,
 xml_detail xml
) 

 Xml template

     <Form>
 <LT004>
<Field>
  <id>txtDate</id>
  <value>3/14/2017</value>
  <tag />
  <visible>true</visible>
    <description>Install Date:</description>
  <comment />
</Field>
<Field>
  <id>txtAge</id>
  <value />
  <tag />
  <visible>true</visible>
   <description>Age:</description>
  <comment />
</Field>
<Field>
  <id>txtCapacity</id>
  **<value>4.000000000000000e+003</value>**
  <tag />
  <visible>true</visible>
    <description> Capacity:</description>
  <comment />
</Field>
<Field>
  <id>Status</id>
  <value>Upgrade Repair Not Marked</value>
  <tag />
  <visible>true</visible>
    <description>Status</description>
  <comment />
</Field>
<Field>
  <id>RemovedDate</id>
  <value />
  <tag />
  <visible>false</visible>
    <description>Date:</description>
  <comment />
 </Field>

  I used the below code to modify but it is not allowing me to use convert   
  function inside that update statement

 UPDATE XML_Capacity 
 SET xml_detail.modify('replace value of (/Form/L004/Field/text())[16] with    (/FormValue/L004/Field/text())[16]')
Where 
xml_detail.value('(/Form/L004/Field/node())[15]', 'varchar(45)') = 'txtCapacity'

Answer 1

我不明白你的陈述

在下面的模板中，我们可以看到字段txtCapacity，该值超出范围值

我们怎么能看到这个？什么是超出范围？

这是常规方法，浮点值存储在XML中。试试这个

SELECT CAST(10.0/3 AS FLOAT(5)) AS SimpleFloat
      ,CAST(10.0/3 AS FLOAT(53)) AS MaxFloat
      ,CAST(10000.0/3 AS FLOAT(5)) AS SimpleFloatBig
      ,CAST(10000.0/3 AS FLOAT(53)) AS MaxFloatBig
FOR XML RAW,ELEMENTS

结果

<row>
  <SimpleFloat>3.3333330e+000</SimpleFloat>
  <MaxFloat>3.333333000000000e+000</MaxFloat>
  <SimpleFloatBig>3.3333333e+003</SimpleFloatBig>
  <MaxFloatBig>3.333333333000000e+003</MaxFloatBig>
</row>

这只是十分强大的科学记数法。您可以使用隐式转换轻松阅读此内容：

DECLARE @xml XML=
'<row>
  <SimpleFloat>3.3333330e+000</SimpleFloat>
  <MaxFloat>3.333333000000000e+000</MaxFloat>
  <SimpleFloatBig>3.3333333e+003</SimpleFloatBig>
  <MaxFloatBig>3.333333333000000e+003</MaxFloatBig>
</row>';
SELECT @xml.value(N'(/row/SimpleFloatBig/text())[1]',N'float(53)')

...返回3333.3333。

在您的示例中，您正在执行某些操作非常危险：您尝试使用其序号（例如'(/Form/L004/Field/node())[15]'）来解决该节点。您应该使用正确的XQuery predicate来获取正确的节点。检查这个完全有效的测试场景：

CREATE DATABASE TestDB;
GO
USE TestDB;
CREATE TABLE XML_Capacity 
( RID int,
 xml_detail xml
);

INSERT INTO XML_Capacity(RID,xml_detail)
VALUES(1,
N'<Form>
  <LT004>
    <Field>
      <id>txtDate</id>
      <value>3/14/2017</value>
      <tag />
      <visible>true</visible>
      <description>Install Date:</description>
      <comment />
    </Field>
    <Field>
      <id>txtAge</id>
      <value />
      <tag />
      <visible>true</visible>
      <description>Age:</description>
      <comment />
    </Field>
    <Field>
      <id>txtCapacity</id>
      <value>4.000000000000000e+003</value>
      <tag />
      <visible>true</visible>
      <description> Capacity:</description>
      <comment />
    </Field>
    <Field>
      <id>Status</id>
      <value>Upgrade Repair Not Marked</value>
      <tag />
      <visible>true</visible>
      <description>Status</description>
      <comment />
    </Field>
    <Field>
      <id>RemovedDate</id>
      <value />
      <tag />
      <visible>false</visible>
      <description>Date:</description>
      <comment />
    </Field>
  </LT004>
</Form>');

 SELECT xml_detail.value(N'(/Form/LT004/Field[(id/text())[1]="txtCapacity"]/value/text())[1]',N'float') 
 FROM XML_Capacity;
 GO

 DECLARE @NewValue FLOAT=12.345;
 UPDATE XML_Capacity
 SET xml_detail.modify(N'replace value of (/Form/LT004/Field[(id/text())[1]="txtCapacity"]/value/text())[1] with sql:variable("@NewValue")')
 WHERE RID=1;


 SELECT xml_detail.value(N'(/Form/LT004/Field[(id/text())[1]="txtCapacity"]/value/text())[1]',N'float') 
 FROM XML_Capacity;

 USE master;
 GO
 DROP DATABASE TestDB;
 GO

返回值为4000， - 修改后为12.345。

使用适当的格式

1 个答案: