java-web JDBC

_Rookie._2024-08-01 19:15

jdbc

java 复制代码

package com.gyk.jdbc;


import com.mysql.jdbc.Driver;
import org.junit.jupiter.api.Test;

import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
 * ClassName: D
 * Package: com.gyk.jdbc
 * Description:
 *
 * @Author Samuel
 * @Create 2024/8/1 13:05
 * @Version 1.0
 */
public class D {
    @Test
    public void m1() throws ClassNotFoundException, SQLException {
        //连接本地 mysql
        //获取驱动类
//        Class.forName("com.mysql.jdbc.Driver");
        //url
        String url = "jdbc:mysql://localhost:3306/test?useSSL=false";
        //username password
        String username = "root";
        String password = "root";
        Connection connection = DriverManager.getConnection(url, username, password);
        System.out.println(connection);
//        DriverManager

    }
}

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/**
 * 在 JDBC 中，PreparedStatement.execute() 方法返回一个布尔值，
 * 表示执行的 SQL 语句是否返回了一个 ResultSet 对象。
 * 对于 INSERT、UPDATE 和 DELETE 语句，execute() 方法通常返回 false，
 * 因为这些语句不会返回 ResultSet 对象。
 */

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executeUpdate
Executes the SQL statement in this PreparedStatement object, which must be an SQL Data Manipulation Language (DML) statement, such as INSERT, UPDATE or DELETE; or an SQL statement that returns nothing, such as a DDL statement.

Returns:

either (1) the row count for SQL Data Manipulation Language (DML) statements or (2) 0 for SQL statements that return nothing

Throws:

SQLException -- if a database access error occurs; this method is called on a closed PreparedStatement or the SQL statement returns a ResultSet object

SQLTimeoutException -- when the driver has determined that the timeout value that was specified by the setQueryTimeout method has been exceeded and has at least attempted to cancel the currently running Statement

java 复制代码

 Boolean aBoolean = preparedStatement.execute();

Returns:
true if the first result is a ResultSet object; 
false if the first result is an update count or there is no result


select * 得到 true （ 15 rows in set (0.00 sec)）

insert update delete 得到false（Query OK, 1 row affected (0.00 sec)）