Update with subquery

Question

I want to update a table with data extracted from a xmltype.
But Oracle extracts only the first value from the subquery.
Am I missing something or this is the expected output...
drop table t
create table t(id number, val varchar2(20));
insert into t(id, val) values (1, null)
insert into t(id, val) values (2, null)
select *
from t
ID     VAL
1     
2     
update t set(val) =
(select t.id from dual)
where id = t.id
select *
from t
ID     VAL
1     1
2     2
update t set(val) =
(select extractValue(
               extract(xmltype('<root>'||
                                   '<node id="1">'||
                                   '<value>1</value>'||
                                   '</node>'||
                                   '<node id="2">'||
                                   '<value>2</value>'||
                                   '</node>'||
                                   '</root>'),
                         '//root/node[@id='||to_char(t.id)||']'),
               '/node/value') from dual)
where id = t.id
select *
from t
ID     VAL
1     1
2     1 -- <-- should be 2!

Answer 1

Hi,
try this way:
SQL> CREATE TABLE tab AS SELECT 1 id,cast(NULL AS VARCHAR2(20)) val FROM dual UNION ALL
  2                      SELECT 2,NULL FROM dual;
Table created.
SQL> DESC tab;
Name                                      Null?    Type
ID                                                 NUMBER
VAL                                                VARCHAR2(20)
SQL>
SQL> SELECT * FROM tab;
        ID VAL                                                                 
         1                                                                     
         2                                                                     
SQL>
SQL> UPDATE tab t
  2  SET val=(
  3      SELECT
  4         extractValue(
  5            extract(
  6               XMLType('<root>
  7                          <node id="1">
  8                            <value>1</value>
  9                          </node>
10                          <node id="2">
11                            <value>2</value>
12                          </node>
13                        </root>')
14               ,'/root/node[@id='||id||']')
15            ,'/node/value') va
16      FROM tab s
17    WHERE t.id=s.id) ;
2 rows updated.
SQL> SELECT * FROM tab;
        ID VAL                                                                 
         1 1                                                                   
         2 2                                                                   
SQL> spool off;btw, you don't need to || every line in xml, and you don't need to do to_char() when using ||
Ants