SQL Server 2008 R2 SQLXML and xpath query filter not working

I have the following schema returning four projects when running sql xml:

<xsd:element name="iati-activities" sql:relation="IATI.ACTIVITIES" sql:key-fields="BUSINESS_UNIT">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element name="iati-activity" sql:relation="IATI.PROJECT_METADATA" sql:relationship="ACTIVITIES_ACTIVITY">
        <xsd:complexType>
          <xsd:sequence>
            <xsd:element name="ProjectId" type="xsd:string" sql:field="PROJECT_ID" sql:key-fields="PROJECT_ID" />
          </xsd:sequence>
        </xsd:complexType>
      </xsd:element>
    </xsd:sequence>
  <xsd:complexType>
</xsd:element>

I want to get:

<iati-activities>
  <iati-activity>
    <ProjectId>00072877</ProjectId>
  </iati-activity>
</iati-activities>

But when running it does not filter. Here is the xpath-query I use:

<root xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <sql:header sql:nullvalue="ISNULL">
    <sql:开发者_StackOverflowparam name="ProjectId">00072877</sql:param>
  </sql:header>
  <sql:xpath-query mapping-schema="activity_schema.xsd">
    iati-activities[iati-activity/ProjectId=$ProjectId]
  </sql:xpath-query>
</root>

This is what I get:

    <iati-activities>
      <iati-activity>
        <ProjectId>00072877</ProjectId>
      </iati-activity>
      <iati-activity>
        <ProjectId>00059626</ProjectId>
      </iati-activity>
      <iati-activity>
        <ProjectId>...</ProjectId>
      </iati-activity>
      <iati-activity>
        <ProjectId>...</ProjectId>
      </iati-activity>
    </iati-activities>

If I use the following query:

<root xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <sql:header sql:nullvalue="ISNULL">
    <sql:param name="ProjectId">00072877</sql:param>
  </sql:header>
  <sql:xpath-query mapping-schema="activity_schema.xsd">
    iati-activities/iati-activity[ProjectId=$ProjectId]
  </sql:xpath-query>
</root>

I get the below without the iati-acitivties element:

<iati-activity>
  <ProjectId>00072877</ProjectId>
</iati-activity>

Any one know what I'm doing wrong?

---

I know what it is... The xpath I was using is only pointing to the element and by selecting the parent of that I get the entire tree under the parent node and not only the filtered one.

It needs to be exported fully and an xslt applied where I define the parent element manually.

<xsl:template match="/">
  <iati-activities version="1.01" GENERATED_DATE="{$GENERATED_DATE}">
    <xsl:for-each select="/iati-activities/iati-activity[ProjectId=$ProjectId]">
      <xsl:copy-of select="." />
    </xsl:for-each>
  </iati-activities>
</xsl:template>