Combining XML into Array

Question

BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE    11.2.0.1.0      Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - ProductionI'm having trouble combining two pieces of sql using xml. I'm building an array of "items" using a select statement that works just fine. (contained_by is the parent of all the children in the array with the same contained by value)
SELECT XMLELEMENT("itemArray", XMLAGG(extract(xml_data,'/item')))    
FROM description_test
WHERE contained_by = 181315;
<itemArray>
   <item>...</item>
   <item>...</item>
   <item>...</item>
</itemArray>Now, when I try to "attach" the parent, I can't seem to get it to work.
SELECT p.naId, XMLCONCAT(extract(p.xml_data,'/fileUnit'),
           XMLAGG(XMLELEMENT("itemArray", extract(c.xml_data,'/item'))))
FROM description_test p --parent,
description_test c --child
WHERE c.contained_by = p.naid;
ORA-00937: not a single-group group function
00937. 00000 -  "not a single-group group function"
SELECT p.naId, XMLCONCAT(extract(p.xml_data,'/fileUnit'),
       XMLAGG(XMLELEMENT("itemArray", extract(c.xml_data,'/item'))))
FROM description_test p, --parent,
description_test c --child
WHERE p.desc_type = 'FU'
AND c.contained_by = p.naid
and rownum < 5
group by p.naid;
ORA-00979: not a GROUP BY expression
00979. 00000 -  "not a GROUP BY expression"what I'm expecting is the following to come back :
<fileUnit>
   <some_data/>
   <more_data/>
   <itemArray>
      <item>...</item>
      <item>...</item>
      <item>...</item>
   </itemArray>
</fileUnit>Not sure why this is not working. If I do the same thing without trying to build the xml array I get the following:
SELECT p.naId, count(c.naid) AS CHILD_COUNT
FROM description_test p,
description_test c
WHERE c.contained_by=p.naid
group by p.naid;
NAID  CHILD_COUNT
135801     25
174634     1
137211     15
136529     30
143455     36
145696     42Help is greatly appreciated. Thanks!!!

Answer 1

Hi,
As always, some sample data would help to understand the problem.
From what you've posted so far, I assume something like this :
create table description_test (
  naid number
, contained_by number
, xml_data xmltype
insert into description_test values (1, null, xmltype('<fileUnit><some_data/><more_data/></fileUnit>'));
insert into description_test values (2, null, xmltype('<fileUnit><some_data/><more_data/></fileUnit>'));
insert into description_test values (3, 1, xmltype('<item>item 1.1</item>'));
insert into description_test values (4, 1, xmltype('<item>item 1.2</item>'));
insert into description_test values (5, 1, xmltype('<item>item 1.3</item>'));
insert into description_test values (6, 2, xmltype('<item>item 2.1</item>'));
insert into description_test values (7, 2, xmltype('<item>item 2.2</item>'));What you're trying to do implies grouping on an XMLType column, which is not possible since the XMLType object doesn't have any MAP or ORDER method.
The solution is to use a subquery, like below.
It also seems that you want insert, not concat :
SQL> select p.naid
  2       , insertchildxml(
  3           p.xml_data
  4         , '/fileUnit'
  5         , 'itemArray'
  6         , (
  7             select xmlelement("itemArray", xmlagg(c.xml_data))
  8             from description_test c
  9             where c.contained_by = p.naid
10           )
11         ) as fileunit
12  from description_test p
13  where p.contained_by is null
14  ;
NAID FILEUNIT
   1 <fileUnit>
       <some_data/>
       <more_data/>
       <itemArray>
         <item>item 1.1</item>
         <item>item 1.2</item>
         <item>item 1.3</item>
       </itemArray>
     </fileUnit>
   2 <fileUnit>
       <some_data/>
       <more_data/>
       <itemArray>
         <item>item 2.1</item>
         <item>item 2.2</item>
       </itemArray>
     </fileUnit>