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Map Relations Specified for Nested Elements

  • Article

A schema can include an msdata:Relationship annotation to explicitly specify the mapping between any two elements in the schema. The two elements specified in msdata:Relationship can be nested in the schema, but do not have to be. The mapping process uses msdata:Relationship in the schema to generate the primary key/foreign key relationship between the two columns.

The following example shows an XML Schema in which the OrderDetail element is a child element of Order. The msdata:Relationship identifies this parent-child relationship and specifies that the OrderNumber column of the resulting Order table is related to the OrderNo column of the resulting OrderDetail table.

<xs:schema id="MyDataSet" xmlns=""
            xmlns:xs="http://www.w3.org/2001/XMLSchema"
            xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">  
<xs:element name="MyDataSet" msdata:IsDataSet="true">  
 <xs:complexType>  
  <xs:choice maxOccurs="unbounded">  
   <xs:element name="Order">  
    <xs:complexType>  
     <xs:sequence>  
       <xs:element name="OrderNumber" type="xs:string" />  
       <xs:element name="EmpNumber" type="xs:string" />  
       <xs:element name="OrderDetail">  
          <xs:annotation>  
           <xs:appinfo>  
            <msdata:Relationship name="OrdODRelation"
                                msdata:parent="Order"
                                msdata:child="OrderDetail"
                                msdata:parentkey="OrderNumber"
                                msdata:childkey="OrderNo"/>  
           </xs:appinfo>  
          </xs:annotation>  
          <xs:complexType>  
            <xs:sequence>  
             <xs:element name="OrderNo" type="xs:string" />  
             <xs:element name="ItemNo" type="xs:string" />  
            </xs:sequence>  
         </xs:complexType>  
       </xs:element>  
     </xs:sequence>  
    </xs:complexType>  
   </xs:element>  
  </xs:choice>  
 </xs:complexType>  
</xs:element>  
</xs:schema>

The XML Schema mapping process creates the following in the DataSet:

  • An Order and an OrderDetail table.

    Order(OrderNumber, EmpNumber)  
OrderDetail(OrderNo, ItemNo)

  • A relationship between the Order and OrderDetail tables. The Nested property for this relationship is set to True because the Order and OrderDetail elements are nested in the schema.

    ParentTable: Order  
ParentColumns: OrderNumber
ChildTable: OrderDetail  
ChildColumns: OrderNo
RelationName: OrdODRelation  
Nested: True

The mapping process does not create any constraints.

See also