Contains operator in a text query

Question

Anybody knows how to query a text contains '>' and '&'?
For exsample, I have following table:
Create table test(a clob);
then insert following records and create a text context index on column a:
insert into test values('test a>b');
insert into test values('test a<b');
create inder test_idx on test(a) indextype is ctxsys.context;
when I issues:
select * from test where contains (a, 'a\>b')>0;
both records are returned
following query returns two records too:
select * from test where contains (a,'a<b')>0;
Also, can anyone tell me how to insert '&test' as a string into test? how to escape those sepcial charactors in contains? Say, what if I need to find all the records contains 'or' ?
Thanks

Answer 1

For inserting a value containing an ampersand (&), set define off. For searching for "or", perhaps instr is more appropriate than contains. For the rest of it, I played around with it and the following seemed to work, but I am not real sure about it. I didn't have any luck with the escape that usually works with regular select statements without contains.
scott@ORA92> Create table test(a clob)
  2  /
Table created.
scott@ORA92> insert into test values('test a>b')
  2  /
1 row created.
scott@ORA92> insert into test values('test a<b')
  2  /
1 row created.
scott@ORA92> set define off
scott@ORA92> insert into test values('&test')
  2  /
1 row created.
scott@ORA92> insert into test values('this or that')
  2  /
1 row created.
scott@ORA92> select * from test
  2  /
A
test a>b
test a<b
&test
this or that
4 rows selected.
scott@ORA92> begin
  2    ctx_ddl.create_preference('my_lexer','BASIC_LEXER');
  3    ctx_ddl.set_attribute('my_lexer','printjoins','>');
  4  end;
  5  /
PL/SQL procedure successfully completed.
scott@ORA92> create index test_idx
  2  on test(a) indextype is ctxsys.context
  3  parameters ('lexer my_lexer')
  4  /
Index created.
scott@ORA92> select * from test where contains (a, '{a>b}')>0
  2  /
A
test a>b
1 row selected.
scott@ORA92> select * from test where contains (a,'{a<b}')>0
  2  /
A
test a<b
1 row selected.
scott@ORA92> select * from test where instr (a,'or')>0
  2  /
A
this or that
1 row selected.
scott@ORA92> exec ctx_ddl.drop_preference('my_lexer')
PL/SQL procedure successfully completed.
scott@ORA92> drop table test
  2  /
Table dropped.