OPENXML (Transact-SQL)
OPENXML provides a rowset view over an XML document. Because OPENXML is a rowset provider, OPENXML can be used in Transact-SQL statements in which rowset providers such as a table, view, or the OPENROWSET function can appear.
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Transact-SQL Syntax Conventions
Syntax
OPENXML( idoc int [ in] , rowpattern nvarchar [ in ] , [ flags byte [ in ] ] )
[ WITH ( SchemaDeclaration | TableName ) ]
Arguments
idoc
Is the document handle of the internal representation of an XML document. The internal representation of an XML document is created by calling sp_xml_preparedocument.rowpattern
Is the XPath pattern used to identify the nodes (in the XML document whose handle is passed in the idoc parameter) to be processed as rows.flags
Indicates the mapping that should be used between the XML data and the relational rowset, and how the spill-over column should be filled. flags is an optional input parameter, and can be one of the following values.Byte value
Description
0
Defaults to attribute-centric mapping.
1
Use the attribute-centric mapping. Can be combined with XML_ELEMENTS. In this case, attribute-centric mapping is applied first, and then element-centric mapping is applied for all columns that are not yet dealt with.
2
Use the element-centric mapping. Can be combined with XML_ATTRIBUTES. In this case, attribute-centric mapping is applied first, and then element-centric mapping is applied for all columns not yet dealt with.
8
Can be combined (logical OR) with XML_ATTRIBUTES or XML_ELEMENTS. In the context of retrieval, this flag indicates that the consumed data should not be copied to the overflow property @mp:xmltext.
SchemaDeclaration
Is the schema definition of the form: ColName ColType [ColPattern | MetaProperty] [, ColNameColType [ColPattern | MetaProperty]...]ColName
Is the column name in the rowset.ColType
Is the SQL Server data type of the column in the rowset. If the column types differ from the underlying xml data type of the attribute, type coercion occurs.ColPattern
Is an optional, general XPath pattern that describes how the XML nodes should be mapped to the columns. If ColPattern is not specified, the default mapping (attribute-centric or element-centric mapping as specified by flags) takes place.The XPath pattern specified as ColPattern is used to specify the special nature of the mapping (in the case of attribute-centric and element-centric mapping) that overwrites or enhances the default mapping indicated by flags.
The general XPath pattern specified as ColPattern also supports the metaproperties.
MetaProperty
Is one of the metaproperties provided by OPENXML. If MetaProperty is specified, the column contains information provided by the metaproperty. The metaproperties allow you to extract information (such as relative position and namespace information) about XML nodes. This provides more information than is visible in the textual representation.
TableName
Is the table name that can be given (instead of SchemaDeclaration) if a table with the desired schema already exists and no column patterns are required.
Remarks
The WITH clause provides a rowset format (and additional mapping information as required) by using either SchemaDeclaration or specifying an existing TableName. If the optional WITH clause is not specified, the results are returned in an edge table format. Edge tables represent the fine-grained XML document structure (such as element/attribute names, the document hierarchy, the namespaces, PIs, and son on) in a single table.
The following table describes the structure of the edge table.
Column name |
Data type |
Description |
|---|---|---|
id |
bigint |
Is the unique ID of the document node. The root element has an ID value 0. The negative ID values are reserved. |
parentid |
bigint |
Identifies the parent of the node. The parent identified by this ID is not necessarily the parent element, but it depends on the NodeType of the node whose parent is identified by this ID. For example, if the node is a text node, the parent of it may be an attribute node. If the node is at the top level in the XML document, its ParentID is NULL. |
nodetype |
int |
Identifies the node type. Is an integer that corresponds to the XML DOM node type numbering. The node types are: 1 = Element node 2 = Attribute node 3 = Text node |
localname |
nvarchar |
Gives the local name of the element or attribute. Is NULL if the DOM object does not have a name. |
prefix |
nvarchar |
Is the namespace prefix of the node name. |
namespaceuri |
nvarchar |
Is the namespace URI of the node. If the value is NULL, no namespace is present. |
datatype |
nvarchar |
Is the actual data type of the element or attribute row, otherwise is NULL. The data type is inferred from the inline DTD or from the inline schema. |
prev |
bigint |
Is the XML ID of the previous sibling element. Is NULL if there is no direct previous sibling. |
text |
ntext |
Contains the attribute value or the element content in text form (or is NULL if the edge table entry does not require a value). |
Examples
A. Using a simple SELECT statement with OPENXML
The following example creates an internal representation of the XML image by using sp_xml_preparedocument. A SELECT statement that uses an OPENXML rowset provider is then executed against the internal representation of the XML document.
The flag value is set to 1. This indicates attribute-centric mapping. Therefore, the XML attributes map to the columns in the rowset. The rowpattern specified as /ROOT/Customer identifies the <Customers> nodes to be processed.
The optional ColPattern (column pattern) parameter is not specified because the column name matches the XML attribute names.
The OPENXML rowset provider creates a two-column rowset (CustomerID and ContactName) from which the SELECT statement retrieves the necessary columns (in this case, all the columns).
DECLARE @idoc int, @doc varchar(1000);
SET @doc ='
<ROOT>
<Customer CustomerID="VINET" ContactName="Paul Henriot">
<Order CustomerID="VINET" EmployeeID="5" OrderDate="1996-07-04T00:00:00">
<OrderDetail OrderID="10248" ProductID="11" Quantity="12"/>
<OrderDetail OrderID="10248" ProductID="42" Quantity="10"/>
</Order>
</Customer>
<Customer CustomerID="LILAS" ContactName="Carlos Gonzlez">
<Order CustomerID="LILAS" EmployeeID="3" OrderDate="1996-08-16T00:00:00">
<OrderDetail OrderID="10283" ProductID="72" Quantity="3"/>
</Order>
</Customer>
</ROOT>';
--Create an internal representation of the XML document.
EXEC sp_xml_preparedocument @idoc OUTPUT, @doc;
-- Execute a SELECT statement that uses the OPENXML rowset provider.
SELECT *
FROM OPENXML (@idoc, '/ROOT/Customer',1)
WITH (CustomerID varchar(10),
ContactName varchar(20));
Here is the result set.
CustomerID ContactName
---------- --------------------
VINET Paul Henriot
LILAS Carlos Gonzlez
If the same SELECT statement is executed with flags set to 2, indicating element-centric mapping, the values of CustomerID and ContactName for both of the customers in the XML document are returned as NULL, because there are not any elements named CustomerID or ContactName in the XML document.
Here is the result set.
CustomerID ContactName
---------- -----------
NULL NULL
NULL NULL
B. Specifying ColPattern for mapping between columns and the XML attributes
The following query returns customer ID, order date, product ID and quantity attributes from the XML document. The rowpattern identifies the <OrderDetails> elements. ProductID and Quantity are the attributes of the <OrderDetails> element. However, OrderID, CustomerID, and OrderDate are the attributes of the parent element (<Orders>).
The optional ColPattern is specified. This indicates the following:
The OrderID, CustomerID, and OrderDate in the rowset map to the attributes of the parent of the nodes identified by rowpattern in the XML document.
The ProdID column in the rowset maps to the ProductID attribute, and the Qty column in the rowset maps to the Quantity attribute of the nodes identified in rowpattern.
Although the element-centric mapping is specified by the flags parameter, the mapping specified in ColPattern overwrites this mapping.
DECLARE @idoc int, @doc varchar(1000);
SET @doc ='
<ROOT>
<Customer CustomerID="VINET" ContactName="Paul Henriot">
<Order OrderID="10248" CustomerID="VINET" EmployeeID="5"
OrderDate="1996-07-04T00:00:00">
<OrderDetail ProductID="11" Quantity="12"/>
<OrderDetail ProductID="42" Quantity="10"/>
</Order>
</Customer>
<Customer CustomerID="LILAS" ContactName="Carlos Gonzlez">v
<Order OrderID="10283" CustomerID="LILAS" EmployeeID="3"
OrderDate="1996-08-16T00:00:00">
<OrderDetail ProductID="72" Quantity="3"/>
</Order>
</Customer>
</ROOT>';
--Create an internal representation of the XML document.
EXEC sp_xml_preparedocument @idoc OUTPUT, @doc;
-- SELECT stmt using OPENXML rowset provider
SELECT *
FROM OPENXML (@idoc, '/ROOT/Customer/Order/OrderDetail',2)
WITH (OrderID int '../@OrderID',
CustomerID varchar(10) '../@CustomerID',
OrderDate datetime '../@OrderDate',
ProdID int '@ProductID',
Qty int '@Quantity');
Here is the result set.
OrderID CustomerID OrderDate ProdID Qty
------------------------------------------------------------------------
10248 VINET 1996-07-04 00:00:00.000 11 12
10248 VINET 1996-07-04 00:00:00.000 42 10
10283 LILAS 1996-08-16 00:00:00.000 72 3
C. Obtaining results in an edge table format
The sample XML document in the following example consists of <Customers>, <Orders>, and <Order_0020_Details> elements. First, sp_xml_preparedocument is called to obtain a document handle. This document handle is passed to OPENXML.
In the OPENXML statement, the rowpattern (/ROOT/Customers) identifies the <Customers> nodes to process. Because the WITH clause is not provided, OPENXML returns the rowset in an edge table format.
Finally the SELECT statement retrieves all the columns in the edge table.
DECLARE @idoc int, @doc varchar(1000);
SET @doc ='
<ROOT>
<Customers CustomerID="VINET" ContactName="Paul Henriot">
<Orders CustomerID="VINET" EmployeeID="5" OrderDate=
"1996-07-04T00:00:00">
<Order_x0020_Details OrderID="10248" ProductID="11" Quantity="12"/>
<Order_x0020_Details OrderID="10248" ProductID="42" Quantity="10"/>
</Orders>
</Customers>
<Customers CustomerID="LILAS" ContactName="Carlos Gonzlez">
<Orders CustomerID="LILAS" EmployeeID="3" OrderDate=
"1996-08-16T00:00:00">
<Order_x0020_Details OrderID="10283" ProductID="72" Quantity="3"/>
</Orders>
</Customers>
</ROOT>';
--Create an internal representation of the XML document.
EXEC sp_xml_preparedocument @idoc OUTPUT, @doc;
-- SELECT statement that uses the OPENXML rowset provider.
SELECT *
FROM OPENXML (@idoc, '/ROOT/Customers')
EXEC sp_xml_removedocument @idoc;