XMLTABLE table function

The XMLTABLE function returns a result table from the evaluation of XQuery expressions, possibly using specified input arguments as XQuery variables. Each sequence item in the result sequence of the row XQuery expression represents a row of the result table.

The schema is SYSIBM. The function name cannot be specified as a qualified name.

xmlnamespaces-declarationSpecifies one or more XML namespace declarations that become part of the static context of the row-xquery-expression-constant and the column-xquery-expression-constant. The set of statically known namespaces for XQuery expressions which are arguments of XMLTABLE is the combination of the pre-established set of statically known namespaces and the namespace declarations specified in this clause. The XQuery prolog within an XQuery expression may override these namespaces.

If xmlnamespaces-declaration is not specified, only the pre-established set of statically known namespaces apply to the XQuery expressions.

row-xquery-expression-constantSpecifies an SQL character string constant that is interpreted as an XQuery expression using supported XQuery language syntax. The constant string is converted directly to UTF-8 without conversion to the database or section code page. The XQuery expression executes using an optional set of input XML values, and returns an output XQuery sequence where a row is generated for each item in the sequence. The value for row-xquery-expression-constant must not be an empty string or a string of all blanks (SQLSTATE 10505).

PASSING

Specifies input values and the manner in which these values are passed to the XQuery expression specified by row-xquery-expression-constant. By default, every unique column name that is in the scope where the function is invoked is implicitly passed to the XQuery expression using the name of the column as the variable name. If an identifier in a specified row-xquery-argument matches an in-scope column name, then the explicit row-xquery-argument is passed to the XQuery expression overriding that implicit column.

BY REF

Specifies that any XML input arguments are, by default, passed by reference. When XML values are passed by reference, the XQuery evaluation uses the input node trees, if any, directly from the specified input expressions, preserving all properties, including the original node identities and document order. If two arguments pass the same XML value, node identity comparisons and document ordering comparisons involving some nodes contained between the two input arguments might refer to nodes within the same XML node tree.

This clause has no impact on how non-XML values are passed. The non-XML values create a new copy of the value during the cast to XML.

row-xquery-argument

Specifies an argument that is to be passed to the XQuery expression that is specified by row-xquery-expression-constant. The method through which row-xquery-argument is used in the XQuery expression depends on whether the argument is specified as an xquery-context-item-expression or an xquery-variable-expression.

If the resulting value is of type XML, it becomes an input-xml-value. A null XML value is converted to an XML empty sequence.
If the resulting value is not of type XML, it must be castable to the XML data type. A null value is converted to an XML empty sequence. The converted value becomes an input-xml-value.

When the row-xquery-expression-constant is evaluated, an XQuery variable is presented with a value equal to input-xml-value and a name specified by the AS clause.

An expression that returns a value that is XML, integer, decimal, or a character or graphic string that is not a LOB. xquery-context-item-expression must not be a character string that is bit data.; xquery-context-item-expression specifies the initial context item for the row-xquery-expression. The value of the initial context item is the result of xquery-context-item-expression cast to XML. xquery-context-item-expression must not be specified more than one time.; Specifies an SQL expression whose value is available to the XQuery expression specified by row-xquery-expression-constant during execution. The expression cannot contain a NEXT VALUE expression, PREVIOUS VALUE expression (SQLSTATE 428F9), or an OLAP function (SQLSTATE 42903). The data type of the expression cannot be DECFLOAT.
AS identifier: Specifies that the value generated by xquery-variable-expression will be passed to row-xquery-expression-constant as an XQuery variable. The variable name will be identifier. The leading dollar sign ($) that precedes variable names in the XQuery language is not included in identifier. The identifier must be a valid XQuery variable name and is restricted to an XML NCName. The identifier must not be greater than 128 bytes in length. Two arguments within the same PASSING clause cannot use the same identifier (SQLSTATE 42711).
BY REF: Indicates that an XML input value is to be passed by reference. When XML values are passed by reference, the XQuery evaluation uses the input node trees, if any, directly from the specified input expressions, preserving all properties, including the original node identities and document order. If two arguments pass the same XML value, node identity comparisons and document ordering comparisons involving some nodes contained between the two input arguments might refer to nodes within the same XML node tree. If BY REF is not specified following an xquery-expression-variable, XML arguments are passed by way of the default passing mechanism that is provided through the syntax that follows the PASSING keyword. This option cannot be specified for non-XML values (SQLSTATE 42636). When a non-XML value is passed, the value is converted to XML; this process creates a copy.

COLUMNS

Specifies the output columns of the result table. If this clause is not specified, a single unnamed column of data type XML is returned by reference, with the value based on the sequence item from evaluating the XQuery expression in the row-xquery-expression-constant (equivalent to specifying PATH '.'). To reference the result column, a column-name must be specified in the correlation-clause following the function.

xml-table-regular-column-definitionSpecifies the output columns of the result table including the column name, data type, XML passing mechanism and an XQuery expression to extract the value from the sequence item for the row

column-nameSpecifies the name of the column in the result table. The name cannot be qualified and the same name cannot be used for more than one column of the table (SQLSTATE 42711).

data-typeSpecifies the data type of the column. See CREATE TABLE for the syntax and a description of types available. A data-type may be used in XMLTable if there is a supported XMLCAST from the XML data type to the specified data-type.

BY REF

Specifies that XML values are returned by reference for columns of data type XML. By default, XML values are returned BY REF. When XML values are returned by reference, the XML value includes the input node trees, if any, directly from the result values, and preserves all properties, including the original node identities and document order. This option cannot be specified for non-XML columns (SQLSTATE 42636). When a non-XML column is processed, the value is converted from XML; this process creates a copy.

default-clauseSpecifies a default value for the column. See CREATE TABLE for the syntax and a description of the default-clause. For XMLTABLE result columns, the default is applied when the processing the XQuery expression contained in column-xquery-expression-constant returns an empty sequence.

PATH column-xquery-expression-constant

Specifies an SQL character string constant that is interpreted as an XQuery expression using supported XQuery language syntax. The constant string is converted directly to UTF-8 without conversion to the database or section code page. The column-xquery-expression-constant specifies an XQuery expression that determines the column value with respect to an item that is the result of evaluating the XQuery expression in row-xquery-expression-constant. Given an item from the result of processing the row-xquery-expression-constant as the externally provided context item, the column-xquery-expression-constant is evaluated, returning an output sequence. The column value is determined based on this output sequence as follows.

If the output sequence contains zero items, the default-clause provides the value of the column.
If an empty sequence is returned and no default-clause was specified, a null value is assigned to the column.
If a non-empty sequence is returned, the value is XMLCAST to the data-type specified for the column. An error could be returned from processing this XMLCAST.

The value for column-xquery-expression-constant must not be an empty string or a string of all blanks (SQLSTATE 10505). If this clause is not specified, the default XQuery expression is simply the column-name.

xml-table-ordinality-column-definitionSpecifies the ordinality column of the result table.

column-name

Specifies the name of the column in the result table. The name cannot be qualified and the same name cannot be used for more than one column of the table (SQLSTATE 42711).

FOR ORDINALITY

Specifies that column-name is the ordinality column of the result table. The data type of this column is BIGINT. The value of this column in the result table is the sequential number of the item for the row in the resulting sequence from evaluating the XQuery expression in row-xquery-expression-constant.

If the evaluation of any of the XQuery expressions results in an error, then the XMLTABLE function returns the XQuery error (SQLSTATE class '10').

Example

List as a table result the purchase order items for orders with a status of 'NEW'.

   SELECT U."PO ID", U."Part #", U."Product Name", 
        U."Quantity", U."Price", U."Order Date"
     FROM PURCHASEORDER P,
        XMLTABLE('$po/PurchaseOrder/item' PASSING P.PORDER AS "po"
                 COLUMNS "PO ID"         INTEGER       PATH '../@PoNum',
                         "Part #"        CHAR(10)      PATH 'partid',
                         "Product Name"  VARCHAR(50)   PATH 'name',
                         "Quantity"      INTEGER       PATH 'quantity',
                         "Price"         DECIMAL(9,2)  PATH 'price',
                         "Order Date"    DATE          PATH '../@OrderDate'
                 ) AS U
      WHERE P.STATUS = 'Unshipped'