MATCHES

Use the MATCHES operator to find all rows in a query table that match a given document. The document must be a plain text, HTML, or XML document.

The MATCHES operator also supports database links. You can identify a remote table or materialized view by appending @dblink to the end of its name. The dblink must be a complete or partial name for a database link to the database containing the remote table or materialized view. (Querying of remote views is not supported.)

This operator requires a CTXRULE index on your set of queries.

When the SVM_CLASSIFIER classifier type is used, MATCHES returns a score in the range 0 to 100; a higher number indicates a greater confidence in the match. Use the label parameter and MATCH_SCORE to obtain this number. Then use the matching score to apply a category-specific threshold to a particular category.

If the SVM_CLASSIFIER type is not used, then this operator returns either 100 (the document matches the criteria) or 0 (the document does not match).

Limitation

If the optimizer chooses to use the functional query invocation with a MATCHES query, your query will fail.

Syntax

MATCHES(
[schema.]column,
document VARCHAR2 or CLOB
[,label INTEGER])
RETURN NUMBER;

column

Specifies the column containing the indexed query set.

document

Specifies the document to be classified. The document can be plain text, HTML, or XML. Binary formats are not supported.

label

Optionally specifies the label that identifies the score generated by the MATCHES operator. Use this label with MATCH_SCORE.

Matches Example

The following example creates a table querytable, and populates it with classification names and associated rules. It then creates a CTXRULE index.

The example enters the MATCHES query with a document string to be classified. The SELECT statement returns all rows (queries) that are satisfied by the document:

create table querytable (classification varchar2(64), text varchar2(4000));
insert into querytable values ('common names', 'smith OR jones OR brown');
insert into querytable values ('countries', 'United States OR Great Britain OR
France');
insert into querytable values ('Oracle DB', 'oracle NEAR database');

create index query_rule on querytable(text) indextype is ctxsys.ctxrule;

SELECT classification FROM querytable WHERE MATCHES(text, 'Smith is a common name
in the United States') > 0;


CLASSIFICATION
----------------------------------------------------------------
common names
countries

“MATCH_SCORE”

“Syntax for CTXRULE Index Type”

CTX_CLS.TRAIN Oracle Text Application Developer’s Guide contains extended examples of simple and supervised classification, which make use of the MATCHES operator.