XMLTABLE



XMLTABLE

Syntax

Description of the illustration xmltable.gif

XMLnamespaces_clause::=

Description of the illustration xml_namespaces_clause.gif

XMLTABLE_options::=

Description of the illustration xmltable_options.gif

XML_passing_clause::=

Description of the illustration xml_passing_clause.gif

XML_table_column::=

Description of the illustration xml_table_column.gif

Purpose

XMLTable maps the result of an XQuery evaluation into relational rows and columns. You can query the result returned by the function as a virtual relational table using SQL.

• The XMLNAMESPACES clause contains a set of XML namespace declarations. These declarations are referenced by the XQuery expression (the evaluated
  XQuery_string), which computes the row, and by the XPath expression in the
  PATH clause of XML_table_column, which computes the columns for the entire
  XMLTable function. If you want to use qualified names in the PATH expressions of the
  COLUMNS clause, then you need to specify the XMLNAMESPACES clause.

• XQuery_string is a complete XQuery expression and can include prolog declarations.

• The expr in the XML_passing_clause is an expression returning an
  XMLType or an instance of a SQL scalar data type that is used as the context for evaluating the XQuery expression. You can specify only one
  expr in the PASSING clause without an identifier. The result of evaluating each
  expr is bound to the corresponding identifier in the
  XQuery_string. If any expr that is not followed by an
  AS clause, then the result of evaluating that expression is used as the context item for evaluating the
  XQuery_string.

• The optional COLUMNS clause defines the columns of the virtual table to be created by
  XMLTable.

  • If you omit the COLUMNS clause, then XMLTable returns a row with a single
    XMLType pseudocolumn named COLUMN_VALUE.

  • The datatype is required unless
    XMLTable is used with XML schema-based storage of XMLType,
    datatype. In this case, if you omit
    datatype, Oracle XML DB infers the data type from the XML schema. If the database is unable to determine the proper type for a node, then a default type of
    VARCHAR2(4000) is used.

  • FOR ORDINALITY specifies that column is to be a column of generated row numbers. There must be at most one
    FOR ORDINALITY clause. It is created as a NUMBER column.

  • The optional PATH clause specifies that the portion of the XQuery result that is addressed by XQuery expression string is to be used as the column content. If you omit
    PATH, then the XQuery expression column is assumed. For example:

    XMLTable(... COLUMNS xyz

    is equivalent to

    XMLTable(... COLUMNS xyz PATH 'XYZ')

    You can use different PATH clauses to split the XQuery result into different virtual-table columns.

  • The optional DEFAULT clause specifies the value to use when the
PATH expression results in an empty sequence. Its expr is an XQuery expression that is evaluated to produce the default value.

  • See Also:

    Oracle XML DB Developer's Guide for more information on the
    XMLTable function, including additional examples, and on XQuery in general

  • Examples

    The following example converts the result of applying the XQuery '/Warehouse' to each value in the
    warehouse_spec column of the warehouses table into a virtual relational table with columns
    Water and Rail:

  • SELECT warehouse_name warehouse,
       warehouse2."Water", warehouse2."Rail"
       FROM warehouses,
       XMLTABLE('/Warehouse'
          PASSING warehouses.warehouse_spec
          COLUMNS
             "Water" varchar2(6) PATH '/Warehouse/WaterAccess',
             "Rail" varchar2(6) PATH '/Warehouse/RailAccess')
          warehouse2;
     
    WAREHOUSE                           Water  Rail
    ----------------------------------- ------ ------
    Southlake, Texas                    Y      N
    San Francisco                       Y      N
    New Jersey                          N      N
    Seattle, Washington                 N      Y