Is it possible to search only one column in a multi column data store?

Question

Assume I create a context index using a multi column datastore for the columns first_name, middle_name, and last_name.
Then I can search all of the columns in the index using contains().
Is there any way to use contains() to just search one of the columns in a multi column datastore - just last_name for instance?
In some cases a want to search all of the columns, in other cases just one of the columns.

Answer 1

Yes, see the doc:
http://download.oracle.com/docs/cd/B14117_01/text.101/b10730/cdatadic.htm#i1006391
If you use the default behaviour, then your column data will be separated by XML-like tags.
<first_name>John</first_name><middle_name>Peter</middle_name><last_name>Doe</last_name>
You would then need to EITHER define each of these as sections, or use "auto_section_group". You can then search on them using
... contains (col, 'peter within middle_name') >0
See example:
SQL> drop table t;
Table dropped.
SQL> create table t (first varchar2(20), middle varchar2(20), last varchar2(20));
Table created.
SQL> insert into t values ('John', 'Peter', 'Doe');
1 row created.
SQL> insert into t values ('Peter', 'Frederik', 'Smith');
1 row created.
SQL> exec ctx_ddl.drop_preference('my_mcds')
PL/SQL procedure successfully completed.
SQL> exec ctx_ddl.create_preference('my_mcds', 'multi_column_datastore')
PL/SQL procedure successfully completed.
SQL> exec ctx_ddl.set_attribute('my_mcds', 'columns', 'first,middle,last')
PL/SQL procedure successfully completed.
SQL> create index ti on t (first) indextype is ctxsys.context
  2  parameters ('datastore my_mcds section group ctxsys.auto_section_group');
Index created.
SQL> select * from t where contains (first, 'peter')>0;
FIRST               MIDDLE            LAST
John               Peter            Doe
Peter               Frederik            Smith
SQL> select * from t where contains (first, 'peter within middle')>0;
FIRST               MIDDLE            LAST
John               Peter            Doe