XML查询的XML查询不起作用

Question

我的XML

<ProductPurchasePlaceDealRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <ClientReference>0000000000GOOA106664</ClientReference>
  <TransactionReference>31966963</TransactionReference>
  <TransactionDescription>NWGHIB00348966</TransactionDescription>
  <TemplateClientReference>00000000000000000FNW</TemplateClientReference>
  <TemplateReference>ISMPURCHASE</TemplateReference>
  <Amount>5862119</Amount>
  <PaymentAmount>0</PaymentAmount>
  <PayerClientReference>00000000000000000FNW</PayerClientReference>
  <PayerAccountType>OMN</PayerAccountType>
  <PayerCurrency>GBP</PayerCurrency>
</ProductPurchasePlaceDealRequest>

我的查询

select
    convert(xml,RequestXML.value('(/ProductPurchasePlaceDealRequest/Amount)[1]', 'varchar(20)'))
from
    WebServicesAudit
where
    id = '9F38D211-9D67-43E4-B0C0-493BA2B84313'
and 
    RequestXML.value('(/ProductPurchasePlaceDealRequest/Amount)[1]', 'varchar(20)') = '5862119'

金额显示为NULL。有什么我想念的吗？ 该字段的基础数据类型是xml，但我认为无论如何我都要转换它，只是加入