Generating XML fragment

Question

Hopefully a quick one that I'm just missing.
I have a child table:
create table files (docid number(9), filename varchar2(200), filetype varchar2(30));
insert into files values (1, '1.pdf', 'primary');
insert into files values (2, '2.pdf', 'primary');
insert into files values (2, '3.pdf', 'secondary');
insert into files values (2, '4.pdf', 'tertiary');
insert into files values (2, '5.pdf', 'pending');
insert into files values (3, '6.pdf', 'secondary');
insert into files values (3, '7.pdf', 'secondary');What I need is an XML fragment to add to the parent document XML to indicate whether a document has a child filetype of some (but not all) of the permitted types.
The rules are:
if a 'primary' exists, create an element <orig>Y</orig>, otherwise create an element <orig>N</orig>
if a 'secondary' exists, create an element <alt>Y</alt>, otherwise create an element <alt>N</alt>
if a 'tertiary' exists, create an element <fin>Y</fin>, otherwise create an element <fin>N</fin>
if a 'pending' exists, do nothing
the result would be something similar to the following for a given docid:
docid 1 : <orig>Y</orig><alt>N</alt><fin>N</fin>
docid 2 : <orig>Y</orig><alt>Y</alt><fin>Y</fin>
docid 3 : <orig>N</orig><alt>Y</alt><fin>N</fin>I've got a brute force solution in hand, but I'm pretty sure there's a more elegant way.

Answer 1

Hi,
Here's one way, if you want to create one fragment at a time for a given DOCID :
SQL> SELECT xmlagg(
  2           case ftype
  3             when 'primary' then xmlelement("orig", ftype_exists)
  4             when 'secondary' then xmlelement("alt", ftype_exists)
  5             when 'tertiary' then xmlelement("fin", ftype_exists)
  6           end
  7         ) as result
  8  FROM (
  9    SELECT t.column_value as ftype
10         , case when count(f.filetype) != 0 then 'Y' else 'N' end as ftype_exists
11    FROM files f
12         RIGHT OUTER JOIN
13           TABLE(
14             sys.odcivarchar2list( 'primary'
15                                 , 'secondary'
16                                 , 'tertiary' )
17           ) t
18             ON t.column_value = f.filetype
19             AND f.docid = 1
20    GROUP BY t.column_value
21  );
RESULT
<orig>Y</orig><alt>N</alt><fin>N</fin>
For multiple DOCID in the same query, a slight modification using a partitioned outer join :
SQL> SELECT docid
  2       , xmlagg(
  3           case ftype
  4             when 'primary' then xmlelement("orig", ftype_exists)
  5             when 'secondary' then xmlelement("alt", ftype_exists)
  6             when 'tertiary' then xmlelement("fin", ftype_exists)
  7           end
  8         ) as result
  9  FROM (
10    SELECT f.docid
11         , t.column_value as ftype
12         , case when count(f.filetype) != 0 then 'Y' else 'N' end as ftype_exists
13    FROM files f
14         PARTITION BY (f.docid)
15         RIGHT OUTER JOIN
16           TABLE(
17             sys.odcivarchar2list( 'primary'
18                                 , 'secondary'
19                                 , 'tertiary' )
20           ) t
21             ON t.column_value = f.filetype
22    GROUP BY f.docid, t.column_value
23  )
24  GROUP BY docid
25  ;
     DOCID RESULT
         1 <orig>Y</orig><fin>N</fin><alt>N</alt>
         2 <orig>Y</orig><fin>Y</fin><alt>Y</alt>
         3 <orig>N</orig><fin>N</fin><alt>Y</alt>