我有以下查询，我希望返回与“我最喜欢的东西”这个短语完全匹配的行
SELECT TestColl.tID, TestMetavalues.*
FROM TestColl, TestMetavalues
WHERE TestColl.tID=TestMetavalues.tID
AND ( (CONTAINS(TestFullText,'(My favorite thing)') > 0 )) ;
但是上面的查询返回了只有“我喜欢的东西”的行以及有“最喜欢的”的行
表TestColl有一个BLOB列 - TestFullText
我希望查询只显示那些具有“我最喜欢的东西”的行
怎么做到这一点？
我试过这些解决方案，但没有运气
Expecting exact results when using contains clause in Oracle
search criteria difference between Like vs Contains() in oracle
试试这个：
SELECT TestColl.tID, TestMetavalues.*
FROM TestColl, TestMetavalues
WHERE TestColl.tID=TestMetavalues.tID
AND TestColl.TestFullText LIKE '%My favorite thing%' ;
我希望查询只显示那些具有“我最喜欢的东西”的行
如果是这样，那么，实际上，你不想要一个简单的
SELECT TestColl.tID, TestMetavalues.*
FROM TestColl, TestMetavalues
WHERE TestColl.tID = TestMetavalues.tID
AND TestFullText = 'My favorite thing';
为什么要使用Oracle Text？
域索引不能像那样工作。我们正在索引源文本中的关键字，所以我们实际上不会存储“我最喜欢的东西”，我们将存储“我的”和“最喜欢的”和“东西”等等。
但是你仍然可以通过使用索引作为初始过滤机制来获得好处，例如
SQL> create table t ( x varchar2(1000));
Table created.
SQL>
SQL> insert into t values ('These are my medium stuff');
1 row created.
SQL> insert into t values ('These are stuff I hate');
1 row created.
SQL> insert into t values ('These are other things');
1 row created.
SQL> insert into t values ('These are semi FAVORITE things');
1 row created.
SQL> insert into t select * from t;
4 rows created.
SQL> insert into t select * from t;
8 rows created.
SQL> insert into t select * from t;
16 rows created.
SQL> insert into t select * from t;
32 rows created.
SQL> insert into t select * from t;
64 rows created.
SQL> insert into t select * from t;
128 rows created.
SQL> insert into t select * from t;
256 rows created.
SQL> insert into t select * from t;
512 rows created.
SQL> --
SQL> -- our special rows
SQL> --
SQL> insert into t values ('These are a few of My Favorite Things');
1 row created.
SQL> insert into t values ('Some other of My Favorite Things');
1 row created.
SQL>
SQL> create index ix on t (x )
2 indextype is ctxsys.context;
Index created.
SQL>
SQL> exec dbms_stats.gather_table_stats('','T')
PL/SQL procedure successfully completed.
SQL>
SQL> set autotrace on explain
SQL> select count(*) from t
2 where CONTAINS(x,'My Favorite Things') > 0;
COUNT(*)
----------
258
1 row selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 2114225437
-------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 26 | 1 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 26 | | |
|* 2 | DOMAIN INDEX | IX | 130 | 3380 | 1 (0)| 00:00:01 |
-------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("CTXSYS"."CONTAINS"("X",'My Favorite Things')>0)
SQL>
SQL> select * from t
2 where CONTAINS(x,'My Favorite Things') > 0
3 and x like '%My Favorite Things%';
X
----------------------------------------------------------------------------------------------------
These are a few of My Favorite Things
Some other of My Favorite Things
2 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 1339481741
------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 6 | 156 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS BY INDEX ROWID| T | 6 | 156 | 3 (0)| 00:00:01 |
|* 2 | DOMAIN INDEX | IX | | | 1 (0)| 00:00:01 |
------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("X" LIKE '%My Favorite Things%' AND "X" IS NOT NULL)
2 - access("CTXSYS"."CONTAINS"("X",'My Favorite Things')>0)
SQL>
SQL>
所以域索引让我们下降到258个候选行，然后额外的LIKE让我们下降到我们想要的2行。