MySQL - 全文搜索
MySQL 全文搜索允许我们搜索存储在 数据库。 在对表的列进行全文搜索之前,我们必须在这些列上创建全文索引。
FTS(全文搜索)能够通过博客、文章等大型文本内容匹配搜索的字符串值。
MySQL 全文搜索
要在 MySQL 表上执行全文搜索,我们在 SQL SELECT 语句的 WHERE 子句中使用 MATCH() 和 AGAINST() 函数。
停用词是句子中常用的词(例如"on"、"the"或"it"),在搜索过程中会被忽略。
在 MySQL 上执行全文搜索的基本语法如下:
SELECT column_name(s) FROM表名 WHERE MATCH(col1, col2, ...) AGAINST(表达式 [search_modifier])
此处,
- MATCH() 函数包含一个或多个以逗号分隔的待搜索列。
- AGAINST() 函数包含用于全文搜索的搜索字符串。
MySQL 全文搜索的要点
以下是有关 MySQL 全文搜索的一些要点 -
- InnoDB 或 MyISAM 表都使用全文索引。全文搜索的单词最小长度为 InnoDB 表的三个字符和 MyISAM 表的四个字符。
- 可以在基于文本的列(CHAR、VARCHAR 或 TEXT 列)上创建全文索引。
- 可以在创建表时使用 CREATE TABLE 语句定义全文索引,也可以稍后使用 ALTER TABLE 或 CREATE INDEX 语句定义全文索引。
- 如果没有全文索引,将大型数据集加载到表中比将数据加载到已有全文索引的表中更快。因此,建议在加载数据后创建索引。
全文搜索的类型
全文搜索有三种类型。如下所示:
- 自然语言全文搜索: 用户可以使用自然人类语言输入搜索查询,无需任何特殊字符或运算符。搜索引擎将检查用户输入的查询,并根据用户的意图返回相关结果。
- 布尔全文搜索:这使我们能够在布尔模式下基于非常复杂的查询以及布尔运算符(例如 +、-、>)执行全文搜索。
- 查询扩展搜索:这可以扩展用户的查询,从而基于自动相关性反馈或盲查询扩展来扩大全文搜索的搜索结果。
创建 MySQL 全文索引
在 MySQL 中,我们可以在创建新表或现有表时在特定列上定义全文索引。这可以通过三种方式实现:
使用 FULLTEXT 关键字
使用 ALTER TABLE 语句
使用 CREATE INDEX 语句
使用 FULLTEXT 关键字
要在创建新表时为列定义全文索引,我们需要在 CREATE TABLE 查询中对该列使用 FULLTEXT 关键字。语法如下:
CREATE TABLE table_name( column1 data_type, column2 data_type, ..., FULLTEXT (column1, column2, ...) );示例
首先创建一个名为 FILMS 的表,并在 NAME 和 DIRECTOR 列上定义全文索引,使用以下查询 -
CREATE TABLE FILMS ( ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) );
现在,让我们使用以下查询将值插入到该表中 -
INSERT INTO FILMS (NAME, DIRECTOR) VALUES ('RRR', 'Directed by Rajamouli'), ('Bahubali', 'Directed by Rajamouli'), ('Avatar', 'Directed by James cameron'), ('Robot', 'Directed by Shankar');
该表将创建为 −
ID | NAME | DIRECTOR |
---|---|---|
1 | RRR | Directed by Rajamouli |
2 | Bahubali | Directed by Rajamouli |
3 | Avatar | Directed by James Cameron |
4 | Robot | Directed by Shankar |
这里,我们使用 MATCH 和 AGAINST 函数,从 FILMS 表中获取 NAME 或 DIRECTOR 列与字符串"Rajamouli"匹配的所有行,如下所示 -
SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Rajamouli');输出
如下面的输出所示,对字符串"Rajamouli"执行了全文搜索,并返回了包含该字符串的行。
ID | NAME | DIRECTOR |
---|---|---|
1 | RRR | Directed by Rajamouli |
2 | Bahubali | Directed by Rajamouli |
使用 ALTER TABLE 语句
在 MySQL 中,我们可以使用 ALTER TABLE 语句在现有表的特定列上创建全文索引。语法如下:-
ALTER TABLE table_name ADD FULLTEXT (column1, column2,...)示例
在此示例中,我们在先前创建的 FILMS 表的 NAME 和 DIRECTOR 列上定义一个名为 FULLTEXT 的全文索引:-
ALTER TABLE FILMS ADD FULLTEXT (NAME, DIRECTOR);
现在,我们从 FILMS 表中检索 NAME 或 DIRECTOR 列与字符串"Shankar"匹配的所有行。
SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Shankar');输出
以下是输出 -
ID | NAME | DIRECTOR |
---|---|---|
4 | Robot | Directed by Shankar |
使用 CREATE INDEX 语句
在 MySQL 中,我们也可以使用 CREATE INDEX 语句为现有表创建全文索引。语法如下:-
CREATE FULLTEXT INDEX index_name ON table_name (index_column1, index_column2,...)示例
我们在 FILMS 表的 NAME 和 DIRECTOR 列上创建名为 INDEX_FULLTEXT 的全文索引 -
CREATE FULLTEXT INDEX INDEX_FULLTEXT ON FILMS (NAME, DIRECTOR);
现在,让我们从 FILMS 表中检索 NAME 或 DIRECTOR 列与字符串值匹配的所有行,如以下查询所示 -
SELECT * FROM FILMS WHERE MATCH(NAME, DIRECTOR) AGAINST ('James Cameron');输出
以下是输出 -
ID | NAME | DIRECTOR |
---|---|---|
3 | Avatar | Directed by James Cameron |
删除 MySQL 全文索引
在 MySQL 中,我们可以使用 ALTER TABLE DROP INDEX 语句从表中删除或删除全文索引。
语法语法如下:
ALTER TABLE table_name DROP INDEX index_name;示例
在以下查询中,我们将删除先前创建的全文索引:
ALTER TABLE FILMS DROP INDEX INDEX_FULLTEXT;验证
让我们通过执行以下查询来验证索引是否已被删除 -
SELECT * FROM FILMS WHERE MATCH(NAME, DIRECTOR) AGAINST ('James Cameron');
正如我们在输出中看到的,NAME 和 DIRECTOR 列上的全文索引已被删除。
ERROR 1191 (HY000): Can't find FULLTEXT index matching the column list
使用客户端程序进行全文搜索
除了使用 MySQL 查询进行全文搜索外,我们还可以使用客户端程序进行全文搜索。
语法
要通过 PHP 程序对 MySQL 数据库执行全文搜索,我们需要使用 mysqli 函数 query() 执行 CREATE TABLE 语句,如下所示 -
$sql = "CREATE TABLE FILMS (ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) )"; $mysqli->query($sql);
要通过 JavaScript 程序对 MySQL 数据库执行全文搜索,我们需要使用 mysql2 库的 query() 函数执行 CREATE TABLE 语句,如下所示 -
sql = "CREATE TABLE FILMS (ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) )"; con.query(sql);
要通过 Java 程序对 MySQL 数据库执行全文搜索,我们需要使用 JDBC 函数 execute() 执行 CREATE TABLE 语句,如下所示 -
String sql = "CREATE TABLE FILMS (ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) )"; statement.execute(sql);
要通过 Python 程序对 MySQL 数据库执行全文搜索,我们需要使用 MySQL Connector/Python 的 execute() 函数执行 CREATE TABLE 语句,如下所示 -
fulltext_search_query = "SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Rajamouli')" cursorObj.execute(fulltext_search_query)
示例
以下是程序 -
$dbhost = 'localhost'; $dbuser = 'root'; $dbpass = 'password'; $dbname = 'TUTORIALS'; $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname); if ($mysqli->connect_errno) { printf("Connect failed: %s
", $mysqli->connect_error); exit(); } // printf('Connected successfully.
'); //创建一个存储全文的表 films。 $sql = "CREATE TABLE FILMS (ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) )"; $result = $mysqli->query($sql); if ($result) { printf("Table created successfully...! "); } //插入数据 $q = "INSERT INTO FILMS (NAME, DIRECTOR) VALUES ('RRR', 'The film RRR is directed by Rajamouli'), ('Bahubali', 'The film Bahubali is directed by Rajamouli'), ('Avatar', 'The film Avatar is directed by James cameron'), ('Robot', 'The film Robot is directed by Shankar')"; if ($res = $mysqli->query($q)) { printf("Data inserted successfully...! "); } //现在显示表记录 $s = "SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Rajamouli')"; if ($r = $mysqli->query($s)) { printf("Table Records: "); while ($row = $r->fetch_assoc()) { printf(" ID: %d, Name: %s, Director: %s", $row["ID"], $row["NAME"], $row["DIRECTOR"]); printf(" "); } } else { printf('Failed'); } $mysqli->close();
输出
获得的输出如下所示 -
Table created successfully...! Data inserted successfully...! Table Records: ID: 1, Name: RRR, Director: The film RRR is directed by Rajamouli ID: 2, Name: Bahubali, Director: The film Bahubali is directed by Rajamouli
var mysql = require("mysql2"); var con = mysql.createConnection({ host: "localhost", user: "root", password: "password", }); //连接到 MySQL con.connect(function (err) { if (err) throw err; // console.log("Connected successfully...!"); // console.log("--------------------------"); sql = "USE TUTORIALS"; con.query(sql); sql = "CREATE TABLE FILMS (ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) )"; con.query(sql); //将数据插入到创建的表中 sql = `INSERT INTO FILMS (NAME, DIRECTOR) VALUES ('RRR', 'The film RRR is directed by Rajamouli'), ('Bahubali', 'The film Bahubali is directed by Rajamouli'), ('Avatar', 'The film Avatar is directed by James cameron'), ('Robot', 'The film Robot is directed by Shankar')`; con.query(sql); //display the table details!... sql = `SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Rajamouli')`; con.query(sql, function (err, result) { if (err) throw err; console.log(result); }); });
输出
获得的输出如下所示 -
[ { ID: 1, NAME: 'RRR', DIRECTOR: 'The film RRR is directed by Rajamouli' }, { ID: 2, NAME: 'Bahubali', DIRECTOR: 'The film Bahubali is directed by Rajamouli' } ]
import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class FulltextSearch { public static void main(String[] args) { String url = "jdbc:mysql://localhost:3306/TUTORIALS"; String username = "root"; String password = "password"; try { Class.forName("com.mysql.cj.jdbc.Driver"); Connection connection = DriverManager.getConnection(url, username, password); Statement statement = connection.createStatement(); System.out.println("Connected successfully...!"); //creating a table that takes fulltext column...! String sql = "CREATE TABLE FILMS (ID int auto_increment not null primary key, NAME varchar(50), DIRECTOR TEXT, FULLTEXT (NAME, DIRECTOR) )"; statement.execute(sql); System.out.println("Table created successfully...!"); //向表中插入数据 String insert = "INSERT INTO FILMS (NAME, DIRECTOR) VALUES ('RRR', 'The film RRR is directed by Rajamouli'), ('Bahubali', 'The film Bahubali is directed by Rajamouli')," + "('Avatar', 'The film Avatar is directed by James cameron'), ('Robot', 'The film Robot is directed by Shankar')"; statement.execute(insert); System.out.println("Data inserted successfully...!"); //displaying the table records...! ResultSet resultSet = statement.executeQuery("SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Rajamouli')"); while (resultSet.next()){ System.out.println(resultSet.getString(1)+" "+resultSet.getString(2)+ " "+resultSet.getString(3)); } connection.close(); } catch (Exception e) { System.out.println(e); } } }
输出
获得的输出如下所示 -
Connected successfully...! Table created successfully...! Data inserted successfully...! 1 RRR The film RRR is directed by Rajamouli 2 Bahubali The film Bahubali is directed by Rajamouli
import mysql.connector # 建立连接 connection = mysql.connector.connect( host='localhost', user='root', password='password', database='tut' ) # 创建游标对象 cursorObj = connection.cursor() fulltext_search_query = f"SELECT * FROM FILMS WHERE MATCH (NAME, DIRECTOR) AGAINST ('Rajamouli');" cursorObj.execute(fulltext_search_query) # 获取所有结果 results = cursorObj.fetchall() # 显示结果 print("Full-text search results:") for row in results: print(row) cursorObj.close() connection.close()
输出
获得的输出如下所示 -
Full-text search results: (1, 'RRR', 'The film RRR is directed by Rajamouli') (2, 'Bahubali', 'The film Bahubali is directed by Rajamouli')