oracle全文索引之WORDLIST PREFERENCE

Oracle全文索引的WORDLIST属性用来设置模糊查询和同词根查询，另外WORDLIST属性还支持通配符查询。
Oracle的WORDLIST属性只有BASIC_WORDLIST一种，下面看一个BASIC_WORDLIST的例子：
1.Stemmer attribute是用来查询用词根的数据
SQL> create table stemmer_tbl(id number primary key,docs clob);
Table created.
SQL> insert into stemmer_tbl values(111,'We are testing the Stemmer attribute option');
1 row created.
SQL> insert into stemmer_tbl values(112,'The girl sang like a frog');
1 row created.
SQL> insert into stemmer_tbl values(113,'My import is committing too often');
1 row created.
SQL> commit;
Commit complete.
--
-- Basic WordList Stemmer attribute
-- This example uses English for Stemming.
-- Language choices are: NULL,ENGLISH,DERIVATIONAL,DUTCH,FRENCH,GERMAN,ITALIAN
-- and SPANISH. By default we use the language of the database. If the
-- database is not one of the listed languages then we choose NULL for stemmer
-- and default for fuzzy
--
SQL> begin
2 Ctx_Ddl.Create_Preference('STEMMER_PREF', 'BASIC_WORDLIST');
3 ctx_ddl.set_attribute('STEMMER_PREF','STEMMER','ENGLISH');
4 end;
5 /
PL/SQL procedure successfully completed.
SQL> create index stemmer_idx on stemmer_tbl ( docs )
2 indextype is ctxsys.context
3 parameters ('Wordlist STEMMER_PREF');
Index created.
SQL> column docs format a20
SQL> select id,docs,score(1) from stemmer_tbl
2 where contains ( docs, '$test',1 ) > 0;
ID DOCS SCORE(1)
---------- -------------------- ----------
111 We are testing the S 4
temmer attribute opt
ion
SQL> select id,docs,score(1) from stemmer_tbl
2 where contains ( docs, '$sing',1) >0;
ID DOCS SCORE(1)
---------- -------------------- ----------
112 The girl sang like a 4
frog
第一个查询是查test的找出testing，这个不太明显；第二个是找词根是sing的数据，找到了sang的这一行数据。