OPENXML (Transact-SQL)

Articol
06/20/2024

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

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.

Transact-SQL syntax conventions

Syntax

OPENXML ( idoc int [ in ]
    , rowpattern nvarchar [ in ]
    , [ flags byte [ in ] ] )
[ WITH ( SchemaDeclaration | TableName ) ]

Arguments

idoc

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

The XPath pattern used to identify the nodes to be processed as rows. The nodes come from the XML document whose handle is passed in the idoc parameter.

flags

Indicates the mapping used between the XML data and the relational rowset, and how the spill-over column is 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. Next, `element-centric` mapping is applied for any remaining columns.
`2`	Use the `element-centric` mapping. Can be combined with `XML_ATTRIBUTES`. In this case, `element-centric` mapping is applied first. Next, `attribute-centric` mapping is applied for any remaining columns.
`8`	Can be combined (logical OR) with `XML_ATTRIBUTES` or `XML_ELEMENTS`. In the context of retrieval, this flag indicates that the consumed data shouldn't be copied to the overflow property `@mp:xmltext`.

SchemaDeclaration

A schema definition of the form: ColNameColType [ ColPattern | MetaProperty ] [ , ColNameColType [ ColPattern | MetaProperty ] ... ]

ColName

The column name in the rowset.
ColType

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

An optional, general XPath pattern that describes how the XML nodes should be mapped to the columns. If ColPattern isn't 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 (for 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

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. These metaproperties provide more information than is visible in the textual representation.

TableName

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 isn't 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 so on) in a single table.

The following table describes the structure of the edge table.

Column name	Data type	Description
`id`	bigint	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 isn't 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 might 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. This value 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. `NULL` if the DOM object doesn't have a name.
`prefix`	nvarchar	The namespace prefix of the node name.
`namespaceuri`	nvarchar	The namespace URI of the node. If the value is `NULL`, no namespace is present.
`data type`	nvarchar	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	The XML ID of the previous sibling element. `NULL` if there's 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 doesn't require a value).

Examples

A. Use a basic 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 value 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 isn't 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's 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 aren't any elements named CustomerID or ContactName in the XML document.

Here's the result set.

CustomerID ContactName
---------- -----------
NULL       NULL
NULL       NULL

B. Specify 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 for the following mappings:

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's 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. Obtain 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 isn't 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;

Examples: Using OPENXML

Partajați prin

OPENXML (Transact-SQL)

Syntax

Arguments

idoc

rowpattern

flags

SchemaDeclaration

TableName

Remarks

Examples

A. Use a basic SELECT statement with OPENXML

B. Specify ColPattern for mapping between columns and the XML attributes

C. Obtain results in an edge table format

Feedback

Resurse suplimentare

Partajați prin

OPENXML (Transact-SQL)

Syntax

Arguments

idoc

rowpattern

flags

SchemaDeclaration

TableName

Remarks

Examples

A. Use a basic SELECT statement with OPENXML

B. Specify ColPattern for mapping between columns and the XML attributes

C. Obtain results in an edge table format

Related content

Feedback

Resurse suplimentare