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How to get better full-text search results in MySQL
Author: Techrepublic.com.com
2006-04-03 11:14:53




Many Internet applications all provide full-text search functions, and users can use a word or word fragment as a query item to locate matching records. Behind the scenes, these programs use the LIKE statement in a SELECT query to perform this query. Although this method works, it is an extremely inefficient method for full-text search, especially when processing large amounts of data. .

MySQL provides a solution to this problem based on the built-in full-text search method. Here, developers simply mark the fields that require full-text search, and then use special MySQL methods to run searches on those fields, which not only improves performance and efficiency (because MySQL indexes these fields to optimize searches) , and enables higher-quality searches because MySQL uses natural language to intelligently rate results to eliminate irrelevant items.

This article will tell you how to perform full-text search in MySQL.

1. Set up the basic table

Start by creating the example table, use the following SQL command:

mysql> CREATE TABLE reviews (id INT(5) PRIMARY KEY NOT NULL AUTO_INCREMENT, data TEXT);

The above command creates a simple music album database (mainly the entire text), and then adds some records to this table:

mysql> INSERT INTO `reviews` (`id`, `data`) VALUES

(1, 'Gingerboy has a new single out called Throwing Rocks. It's great!');

mysql> INSERT INTO `reviews` (`id`, `data`) VALUES

(2, 'Hello all, I really like the new Madonna single.

One of the hottest tracks currently playing... I've been listening to it all day');

mysql> INSERT INTO `reviews` (`id`, `data`)

VALUES (3, 'Have you heard the new band Hotter Than Hell?

They have five members and they burn their instruments when they play in concerts.

These guys totally rock! Like, awesome, dude!');

Verify the correct entry of data:

mysql> SELECT * FROM reviews;

+----+---------------- ----------------------------+

| id | data                                                                        +---------------------------------------------+

| 1 | Gingerboy has a new single out called... |

| 2 | Hello all, I really like the new Madon... |

| 3 | Have you heard the new band Hotter Than... |

+----+----------------------------- ---------------+

3 rows in set (0.00 sec)

2. Define the full-text search field

Next , define the fields you want to index for full-text search

mysql> ALTER TABLE reviews ADD FULLTEXT INDEX (data);

Query OK, 3 rows affected (0.21 sec)

Records: 3 Duplicates: 0 Warnings: 0

Use the SHOW INDEXES command to check that the index has been added:

mysql> SHOW INDEXES FROM reviews;

+--- ------+---------------+--------+------+---------- -+---------+

| Table | Column_name | Packed | Null | Index_type | Comment |

----------+-- -------------+--------+------+----------------+------ --+

| reviews | id | NULL | BTREE |

| reviews | data | NULL | YES | FULLTEXT |

+----- ----+---------------+--------+------+------------+ ---------+

2 rows in set (0.01 sec)

3. Run full-text search

When you have the data and index, You can use MySQL's full-text search. The simplest full-text search method is the SELECT query with the MATCH...AGAINST statement. The following is a simple example to find records containing the word "single":

mysql> SELECT id FROM reviews WHERE MATCH (data) AGAINST ('single');+----+

| id |

+----+

| 1 |

| 2 |

+----+

2 rows in set (0.00 sec)

Here, MATCH () compares the text in the field passed to it as a parameter with the parameters passed to AGAINST(). If there is a match, it is returned in the normal way. Note that you can pass more than one field to MATCH() - just comma-separate the list of fields.

When MySQL receives a full-text search request, it scores each record internally, with unmatched records getting a score of zero, and "more relevant" records getting a higher score than "less relevant" ones. recorded relatively higher scores.Relevance is determined by a series of MySQL distinction criteria. Check the MySQL user manual for more information.

To see the score of each record, just return the MATCH() method as part of the result set, as shown below:

mysql> SELECT id, MATCH (data) AGAINST ( 'rock') FROM reviews;

+----+--------------------------------- +

| id | MATCH (data) AGAINST ('rock') |

+----+---------------- ---------------+

| 1 | 0 |

| 2 | 0 |          1.3862514533815 |

+----+----------------------------------+

3 rows in set (0.00 sec)

4. Use logical search modifiers (Boolean search modifiers)

You can also use logical search modifiers to conduct a more precise search, which is done in the AGAINST statement Add the special IN BOOLEAN MODE modifier to achieve this. In the following example, records containing the word "single" but not "Madonna" will be found:

mysql> SELECT id FROM reviews WHERE MATCH (data) AGAINST ('+single -madonna' IN BOOLEAN MODE);

+----+

| id |

+----+

| 1 |

+----+

1 row in set (0.00 sec)

This search feature is usually used to search for word fragments (instead of Complete word), this can be achieved by using the * (asterisk) operator in the IN BOOLEAN MODE statement. The following example shows how to find records containing "hot" in the word:

mysql> SELECT id FROM reviews WHERE MATCH (data) AGAINST ('hot*' IN BOOLEAN MODE);+----+

| id |

+----+

| 3 |

| 2 |

+----+

2 rows in set (0.00 sec)

You can also use This method finds at least one parameter passed to AGAINST. The following example finds records that contain at least one of the words "hell" and "rocks":

mysql> SELECT id FROM reviews WHERE MATCH ( data) AGAINST ('hell rocks' IN BOOLEAN MODE);

+----+

| id |

+----+

| 1 |

| 3 |

+----+

2 rows in set (0.00 sec)

These examples above It demonstrates a more effective method for full-text search compared to the traditional SELECT...LIKE statement. You can try this method the next time you need to write a MySQL database search interface.

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www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/318360.htmlTechArticleHow to get better full-text search results in MySQL Author: Techrepublic.com.com 2006-04-0311: 14:53 Many Internet applications provide full-text search capabilities, and users can use a...