How to create tagging attributes

Question

Hello,
this are two questions in one...
1. how do I create "empty" attributes like this: <tt>&lt;Element Attribute></tt>?
2. How do I trigger the creation of the attribute by a value from DB? SQL> WITH my_data AS
  2         (SELECT 'test1' AS element_name
  3               , 0 AS tag_attrib
  4            FROM DUAL
  5          UNION ALL
  6          SELECT 'test2' AS element_name
  7               , 1 AS tag_attrib
  8            FROM DUAL)
  9  SELECT XMLELEMENT( element_name )
10       , XMLELEMENT( element_name
11                   , case when tag_attrib = 1 then xmlattributes( 1 as "tag_attrib" ) else null end
12                    )
13    FROM my_data;
                 , case when tag_attrib = 1 then xmlattributes( 1 as "tag_attrib" ) else null end
FEHLER in Zeile 11:
ORA-00907: missing right parenthesis
SQL>

Answer 1

1. how do I create "empty" attributes like this: <tt>&lt;Element Attribute></tt>?That's not valid.
Did you mean :
<Elem Attr=""> ?
2. How do I trigger the creation of the attribute by a value from DB? By moving the CASE statement into XMLAttributes.
XMLAttributes doesn't generate attribute for NULL values :
SQL> WITH my_data(element_name, tag_attrib) AS (
  2    SELECT 'test1', 0 FROM DUAL UNION ALL
  3    SELECT 'test2', 1 FROM DUAL
  4  )
  5  SELECT XMLSerialize(content
  6           XMLElement( element_name
  7           , XMLAttributes(
  8               case when tag_attrib = 1
  9                    then tag_attrib
10               end as "tag_attrib"
11             )
12           )
13           as varchar2(2000)
14           indent
15         )
16  FROM my_data;
XMLSERIALIZE(CONTENTXMLELEMENT
<ELEMENT_NAME/>
<ELEMENT_NAME tag_attrib="1"/>