3 Creating Your Query Syntax

See the section, "Querying with the CONTAINS Operator" for information about how to use the CONTAINS operator in query statements.

Querying Within Attribute Sections

You can query within attribute sections when you index with either XML_SECTION_GROUP or AUTO_SECTION_GROUP as your section group type.

Assume you have an XML document as follows:

<book title="Tale of Two Cities">It was the best of times.</book>

You can define the section title@book as the attribute section title. You can do so with the CTX_DLL.Add_Attr_Section procedure or dynamically after indexing with ALTER INDEX.

Note: When you use the AUTO_SECTION_GROUP to index XML documents, the system automatically creates attribute sections and names them in the form attribute@tag.

If you use the XML_SECTION_GROUP, you can name attribute sections anything with CTX_DDL.Add_Attr_Section.

To search on Tale within the attribute section title, issue the following query:

WHERE CONTAINS (...,'Tale WITHIN title', ...)

Using XML_SECTION_GROUP and add_attr_section to Aid Querying

Consider an XML file that defines the BOOK tag with a TITLE attribute as follows:

<BOOK TITLE="Tale of Two Cities"> 
It was the best of times. </BOOK> 
<Author="Charles Dickens">
Born in England in the town, Stratford_Upon_Avon </Author>

Recall the CTX_DDL.Add_Attr_Section syntax is:

CTX_DDL.Add_Attr_Section ( group_name, section_name, tag );

To define the title attribute as an attribute section, create an XML_SECTION_GROUP and define the attribute section as follows:

ctx_ddl_create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_attr_section('myxmlgroup', 'booktitle', 'book@title');
ctx_ddl.add_attr_section('myxmlgroup', 'authors', 'author');
end;

When you define the TITLE attribute section as such and index the document set, you can query the XML attribute text as follows:

... WHERE CONTAINS (...,'Cities WITHIN booktitle', ....)...

When you define the AUTHOR attribute section as such and index the document set, you can query the XML attribute text as follows:

... WHERE 'England WITHIN authors'

interMedia Text Example 4: Querying a... Document

This example does the following:

1. Creates and populates table res_xml

2. Creates an index, section_group, and preferences

3. Paramaterizes the preferences

4. Runs a test query against res_xml

   drop table res_xml;
   
   CREATE TABLE res_xml (
     pk            NUMBER PRIMARY KEY ,
     text          CLOB
     ) ;
   
   insert into res_xml values(111,
     'ENTITY chap8 "Chapter 8, <q>Keeping it Tidy: the XML Rule Book </q>"> this is 
   the document section');
   commit;
   
   ---
   --- script to create index on res_xml
   ---
   
   --- cleanup, in case we have run this before
   DROP INDEX res_index ;
   EXEC CTX_DDL.DROP_SECTION_GROUP ( 'res_sections' ) ;
   
   --- create a section group
   BEGIN
     CTX_DDL.CREATE_SECTION_GROUP ( 'res_sections', 'XML_SECTION_GROUP' ) ;
     CTX_DDL.ADD_FIELD_SECTION ( 'res_sections', 'chap8', '<q>') ;
   END ;
   /
   
   begin
     ctx_ddl.create_preference
       (
         preference_name => 'my_basic_lexer',
         object_name     => 'basic_lexer'
       );
     ctx_ddl.set_attribute
       (
         preference_name => 'my_basic_lexer',
         attribute_name  => 'index_text',
         attribute_value => 'true'
       );
     ctx_ddl.set_attribute
       (
         preference_name => 'my_basic_lexer',
         attribute_name  => 'index_themes',
         attribute_value => 'false');
   end;
   /
   
   CREATE INDEX res_index
     ON res_xml(text)
     INDEXTYPE IS ctxsys.context 
     PARAMETERS ( 'lexer my_basic_lexer SECTION GROUP res_sections' ) ;
   
   

Test the above index with a test query, such as:

SELECT pk FROM res_xml WHERE CONTAINS( text, 'keeping WITHIN chap8' )>0 ;

interMedia Example 5: Creating an Index and Performing a Text Query

Creating Table explain_ex to Use in this Example

drop table explain_ex; 
 
create table explain_ex 
  ( 
    id        number primary key,
    text      varchar(2000)
  ); 
 
insert into explain_ex ( id, text )
  values ( 1, 'thinks thinking thought go going goes gone went' || chr(10) ||
              'oracle orackle oricle dog cat bird'              || chr(10) ||
              'President Clinton' ); 
insert into explain_ex ( id, text )
  values ( 2, 'Last summer I went to New England'               || chr(10) ||
              'I hiked a lot.'                                  || chr(10) ||
              'I camped a bit.' ); 
commit;

Creating an Index for themes

begin 
  Ctx_Ddl.Drop_Preference ('my_lexer'); 
end; 
/ 
begin 
  Ctx_Ddl.Create_Preference ( 'my_lexer', 'basic_lexer'); 
  Ctx_Ddl.Set_Attribute     ( 'my_lexer', 'index_text',   'true' );

  /* Experiment with 'index_themes' = 'false' */
  Ctx_Ddl.Set_Attribute     ( 'my_lexer', 'index_themes', 'true' );
end;
/

begin
  Ctx_Ddl.Drop_Stoplist ( 'my_stoplist' );
end;
/

begin
  Ctx_Ddl.Create_Stoplist ( 'my_stoplist' );
  Ctx_Ddl.Add_Stopword
    (
      stoplist_name => 'my_stoplist',
      stopword      => 'because'
    );
  Ctx_Ddl.Add_Stopword ( 'my_stoplist', 'and' );
  Ctx_Ddl.Add_Stopword ( 'my_stoplist', 'in' );
  Ctx_Ddl.Add_Stopword ( 'my_stoplist', 'to' );
  Ctx_Ddl.Add_Stopword ( 'my_stoplist', 'a' );
  Ctx_Ddl.Add_Stopword ( 'my_stoplist', 'I' );
end;
/

drop index explain_ex_text;
select err_text from ctx_user_index_errors;
create index explain_ex_text on explain_ex ( text ) 
  indextype is ctxsys.context
  parameters ( 'lexer my_lexer stoplist ctxsys.empty_stoplist' );
select err_text from ctx_user_index_errors;

begin 
  Ctx_Ddl.Drop_Preference ('my_lexer'); 
  Ctx_Ddl.Drop_Stoplist ( 'my_stoplist' );
end; 
/ 

Text Query Using "ABOUT" in the Text Query Expression

Set Define Off
select text 
  from explain_ex
  WHERE CONTAINS ( text,
  '( $( think & go ) , ?oracle ) & ( dog , ( cat & bird ) ) & about(mammal
                                                    during Bill Clinton)' ) > 0;

select text 
  from explain_ex
  WHERE CONTAINS ( text, 'about ( camping and hiking in new england )'  ) > 0;