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Name

XMLType.getRootElement — Returns top-level element of the given instance (NULL for fragment)

Synopsis

XMLType.getRootElement ( );
 

Description

If the given instance is well-formed then this function will return the top-level element of the document that is stored within the instance. If the given instance is a fragment then NULL will be returned because there may be no top-level elements or too many of them.

Note that in spite of this functions name this function actually returns the a top-level node rather than not a root node. According to the W3C XPATH standards, the root element is an implicit node whose children are top-level elements, comments, processing instructions and maybe text nodes. E.g. if a correct HTML document is started by tag <HTML> and ended by corresponding </HTML> tag then the only top-level node is the "HTML " element node and this node is a single child of the root node.

If the given instance is well-formed then the function returns a top-level element of the document that is stored in the instance. If the given instance is fragment then NULL is returned, because there may be no top-level elements or too many of them.

If the given instance is schema-based then the returned instance is based on the same schema.

Return Types

The function returns an XMLType instance.

Examples

Example 24.552. A table with an XMLType column

First select statement lists well-formed documents; second one lists the only fragment in the table. 

create table TEST_XMLS  (I integer primary key, XMLVAL XMLType);
insert into TEST_XMLS  values (1, XMLType('<emp><empno>221</empno><ename>John</ename></emp>'));
insert into TEST_XMLS  values (2, XMLType('<po><pono>331</pono><poname>PO_1</poname></po>'));
insert into TEST_XMLS  values (3, XMLType('<oil-rig
xml:id="14a_04" water="0.413"/><oil-rig
xml:id="14b_04" water="0.402"/>'));

select e.I, e.XMLVAL.getRootElement().getClobVal()
  from TEST_XMLS as e
  where e.XMLVAL.getRootElement() is not null
I                 callret
INTEGER NOT NULL  NVARCHAR
_______________________________________________________________________________

1                 <emp><empno>221</empno><ename>John</ename></emp>
2                 <po><pono>331</pono><poname>PO_1</poname></po>

2 Rows. -- 00000 msec.

select e.I, e.XMLVAL.getClobVal()
  from TEST_XMLS as e
  where e.XMLVAL.getRootElement() is null
I                 callret
INTEGER NOT NULL  NVARCHAR
_______________________________________________________________________________

3                 <oil-rig
xml:id="14a_05" water="0.413" /><oil-rig
xml:id="14b_05" water="0.402" />

1 Rows. -- 00000 msec.

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