Specifying Axes in XPath Queries (SQLXML 4.0)

Articolo
12/15/2008

The following examples show how axes are specified in XPath queries.

The XPath queries in these examples are specified against the mapping schema contained in SampleSchema1.xml. For information about this sample schema, see Sample Annotated XSD Schema for XPath Examples (SQLXML 4.0).

Examples

A. Retrieve child elements of the context node

The following XPath query selects all the <Contact> child elements of the context node:

/child::Contact

In the query, child is the axis and Contact is the node test (TRUE if Contact is an <element> node, because <element> is the primary node type associated with the child axis).

The child axis is the default. Therefore, the query can be written as:

/Contact

To test the XPath query against the mapping schema

Copy the sample schema code and paste it into a text file. Save the file as SampleSchema1.xml.
Create the following template (XPathAxesSampleA.xml) and save it in the directory where SampleSchema1.xml was saved.
```
<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <sql:xpath-query mapping-schema="SampleSchema1.xml">
    /Contact
  </sql:xpath-query>
</ROOT>
```
The directory path specified for the mapping schema (SampleSchema1.xml) is relative to the directory where the template is saved. An absolute path also can be specified, for example:
```
mapping-schema="C:\MyDir\SampleSchema1.xml"
```
Create and use the SQLXML 4.0 Test Script (Sqlxml4test.vbs) to execute the template.

For more information, see Using ADO to Execute SQLXML 4.0 Queries.

Here is the partial result set of the template execution:

<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql"> 
  <Contact ContactID="1" LastName="Achong" FirstName="Gustavo" Title="Mr." /> 
  <Contact ContactID="2" LastName="Abel" FirstName="Catherine" Title="Ms." /> 
  <Contact ContactID="3" LastName="Abercrombie" FirstName="Kim" Title="Ms." /> 
  <Contact ContactID="4" LastName="Acevedo" FirstName="Humberto" Title="Sr." />
  ...
</ROOT>

B. Retrieve grandchildren of the context node

The following XPath query selects all the <Order> element children of the <Customer> element children of the context node:

/child::Customer/child::Order

In the query, child is the axis and Customer and Order are the node tests (these node tests are TRUE if Customer and Order are <element> nodes, because the <element> node is the primary node for the child axis). For each node matching <Customer>, the nodes matching <Orders> are added to the result. Only <Order> is returned in the result set.

The child axis is the default. Therefore, the query can be specified as:

/Customer/Order

To test the XPath query against the mapping schema

Copy the sample schema code and paste it into a text file. Save the file as SampleSchema1.xml.
Create the following template (XPathAxesSampleB.xml) and save it in the directory where:
```
<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <sql:xpath-query mapping-schema="SampleSchema1.xml">
    /Customer/Order
  </sql:xpath-query>
</ROOT>
```
The directory path specified for the mapping schema (SampleSchema1.xml) is relative to the directory where the template is saved. An absolute path also can be specified, for example:
```
mapping-schema="C:\MyDir\SampleSchema1.xml"
```
Create and use the SQLXML 4.0 Test Script (Sqlxml4test.vbs) to execute the template.

For more information, see Using ADO to Execute SQLXML 4.0 Queries.

Here is the partial result set of the template execution:

<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <Order SalesOrderID="Ord-43860" SalesPersonID="280" 
         OrderDate="2001-08-01T00:00:00" 
         DueDate="2001-08-13T00:00:00" 
         ShipDate="2001-08-08T00:00:00">
  <OrderDetail ProductID="Prod-729" UnitPrice="226.8571" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-732" UnitPrice="440.1742" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-738" UnitPrice="220.2496" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-753" UnitPrice="2576.3544" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-756" UnitPrice="1049.7528" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-758" UnitPrice="1049.7528" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-761" UnitPrice="503.3507" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-762" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-763" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-765" UnitPrice="503.3507" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-768" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-770" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  </Order>
   ...
</ROOT>

If the XPath query is specified as Customer/Order/OrderDetail, from each node matching <Customer> the query navigates to its <Order> elements. And for each node matching <Order>, the query adds the nodes <OrderDetail> to the result. Only <OrderDetail> is returned in the result set.

C. Use .. to specify the parent axis

The following query retrieves all the <Order> elements with a parent <Customer> element with a CustomerID attribute value of 1. The query uses the child axis in the predicate to find the parent of the <Order> element.

/child::Customer/child::Order[../@CustomerID="1"]

The child axis is the default axis. Therefore, the query can be specified as:

/Customer/Order[../@CustomerID="1"]

The XPath query is equivalent to:

/Customer[@CustomerID="1"]/Order.

[!NOTA] The XPath query /Order[../@CustomerID="1"] will return an error because there is no parent of <Order>. Although there may be elements in the mapping schema that contain <Order>, the XPath did not begin at any of them; consequently, <Order> is considered to be the top-level element type in the document.

To test the XPath query against the mapping schema

Copy the sample schema code and paste it into a text file. Save the file as SampleSchema1.xml.
Create the following template (XPathAxesSampleC.xml) and save it in the directory where:
```
<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <sql:xpath-query mapping-schema="SampleSchema1.xml">
    /Customer/Order[../@CustomerID="1"]
  </sql:xpath-query>
</ROOT>
```
The directory path specified for the mapping schema (SampleSchema1.xml) is relative to the directory where the template is saved. An absolute path also can be specified, for example:
```
mapping-schema="C:\MyDir\SampleSchema1.xml"
```
Create and use the SQLXML 4.0 Test Script (Sqlxml4test.vbs) to execute the template.

For more information, see Using ADO to Execute SQLXML 4.0 Queries.

Here is the partial result set of the template execution:

<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <Order SalesOrderID="Ord-43860" SalesPersonID="280" 
         OrderDate="2001-08-01T00:00:00" 
         DueDate="2001-08-13T00:00:00" 
         ShipDate="2001-08-08T00:00:00">
  <OrderDetail ProductID="Prod-729" UnitPrice="226.8571" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-732" UnitPrice="440.1742" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-738" UnitPrice="220.2496" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-753" UnitPrice="2576.3544" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-756" UnitPrice="1049.7528" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-758" UnitPrice="1049.7528" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-761" UnitPrice="503.3507" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-762" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-763" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-765" UnitPrice="503.3507" 
               OrderQty="2" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-768" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  <OrderDetail ProductID="Prod-770" UnitPrice="503.3507" 
               OrderQty="1" UnitPriceDiscount="0" /> 
  </Order>
   ...
</Order>
</ROOT>

D. Specify the attribute axis

The following XPath query selects all the <Customer> child elements of the context node with a CustomerID attribute value of 1:

/child::Customer[attribute::CustomerID="1"]

In the predicate attribute::CustomerID, attribute is the axis and CustomerID is the node test (if CustomerID is an attribute the node test is TRUE, because the <attribute> node is the primary node for the attribute axis).

A shortcut to the attribute axis (@) can be specified, and because child is the default axis, it can be omitted from the query:

/Customer[@CustomerID="1"]

To test the XPath query against the mapping schema

Copy the sample schema code and paste it into a text file. Save the file as SampleSchema1.xml.
Create the following template (XPathAxesSampleD.xml) and save it in the directory where SampleSchema1.xml is saved.
```
<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <sql:xpath-query mapping-schema="SampleSchema1.xml">
    child::Customer[attribute::CustomerID="1"]
  </sql:xpath-query>
</ROOT>
```
The directory path specified for the mapping schema (SampleSchema1.xml) is relative to the directory where the template is saved. An absolute path also can be specified, for example:
```
mapping-schema="C:\MyDir\SampleSchema1.xml"
```
Create and use the SQLXML 4.0 Test Script (Sqlxml4test.vbs) to execute the template.

For more information, see Using ADO to Execute SQLXML 4.0 Queries.

Here is the partial result set of the template execution:

<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
  <Customer CustomerID="1" SalesPersonID="280" 
            TerritoryID="1" AccountNumber="1" 
            CustomerType="S" Orders="Ord-43860 Ord-44501 Ord-45283 Ord-46042">
    <Order SalesOrderID="Ord-43860" SalesPersonID="280" 
           OrderDate="2001-08-01T00:00:00" 
           DueDate="2001-08-13T00:00:00" 
           ShipDate="2001-08-08T00:00:00">
       <OrderDetail ProductID="Prod-729" UnitPrice="226.8571" 
                    OrderQty="1" UnitPriceDiscount="0" /> 
       <OrderDetail ProductID="Prod-732" UnitPrice="440.1742" 
                    OrderQty="1" UnitPriceDiscount="0" /> 
       <OrderDetail ProductID="Prod-738" UnitPrice="220.2496" 
                    OrderQty="1" UnitPriceDiscount="0" /> 
      ... 
    </Order>
   ...
  </Customer>
</ROOT>

Condividi tramite

Specifying Axes in XPath Queries (SQLXML 4.0)

Examples

A. Retrieve child elements of the context node

B. Retrieve grandchildren of the context node

C. Use .. to specify the parent axis

D. Specify the attribute axis

Risorse aggiuntive