Question

怎样使用jdbc访问mysql数据库

Answer 1

JDBC连接MYSQL数据库：

package cn.outofmemory.test;

import java.sql.Connection;
import java.sql.DriverManager;

public class Mysql {
public static void main(String arg[]) {
try {
Connection con = null; //定义一个MYSQL链接对象
Class.forName("com.mysql.jdbc.Driver").newInstance(); //MYSQL驱动
con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test", "root", "root"); //链接本地MYSQL
System.out.print("yes");
} catch (Exception e) {
System.out.print("MYSQL ERROR:" + e.getMessage());
}

}
}

Class.forName("com.mysql.jdbc.Driver").newInstance(); 我们链接的是MYSQL数据库，所以需要一个MYSQL的数据库驱动，如果你的环境中没有安装，
可以下载：mysql-connector-java-5.1.17-bin.jar JAR包，然后放进jdk1.6.0_37\jre\lib\ext 重启eclispe 就可以在JRE系统库中看到。

con = DriverManager.getConnection;("jdbc:mysql://127.0.0.1:3306/test", "root", "root"); 是链接数据库的语句，
返回Connection con;对象。参数格式：("jdbc:mysql://ip:端口/数据库名称", 用户名,密码)

写入一条数据

package main;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class Mysql {

/**
* 入口函数
* @param arg
*/
public static void main(String arg[]) {
try {
Connection con = null; //定义一个MYSQL链接对象
Class.forName("com.mysql.jdbc.Driver").newInstance(); //MYSQL驱动
con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test", "root", "root"); //链接本地MYSQL

Statement stmt; //创建声明
stmt = con.createStatement();

//新增一条数据
stmt.executeUpdate("INSERT INTO user (username, password) VALUES ('init', '123456')");
ResultSet res = stmt.executeQuery("select LAST_INSERT_ID()");
int ret_id;
if (res.next()) {
ret_id = res.getInt(1);
System.out.print(ret_id);
}

} catch (Exception e) {
System.out.print("MYSQL ERROR:" + e.getMessage());
}

}
}

stmt.executeUpdate INSERT; DELETE; UPDATE;语句都用executeUpdate函数来操作
stmt.executeQuery SELECT;语句都用stmt.executeQuery函数来操作
ResultSet res = stmt.executeQuery;("select LAST;_INSERT_ID()");
查询最后插入数据的ID号，返回ResultSet res;对象

删除和更新数据
package main;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class Mysql {

/**
* 入口函数
* @param arg
*/
public static void main(String arg[]) {
try {
Connection con = null; //定义一个MYSQL链接对象
Class.forName("com.mysql.jdbc.Driver").newInstance(); //MYSQL驱动
con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test", "root", "root"); //链接本地MYSQL

Statement stmt; //创建声明
stmt = con.createStatement();

//新增一条数据
stmt.executeUpdate("INSERT INTO user (username, password) VALUES ('init', '123456')");
ResultSet res = stmt.executeQuery("select LAST_INSERT_ID()");
int ret_id;
if (res.next()) {
ret_id = res.getInt(1);
System.out.print(ret_id);
}

//删除一条数据
String sql = "DELETE FROM user WHERE id = 1";
long deleteRes = stmt.executeUpdate(sql); //如果为0则没有进行删除操作，如果大于0，则记录删除的条数
System.out.print("DELETE:" + deleteRes);

//更新一条数据
String updateSql = "UPDATE user SET username = 'xxxx' WHERE id = 2";
long updateRes = stmt.executeUpdate(updateSql);
System.out.print("UPDATE:" + updateRes);

} catch (Exception e) {
System.out.print("MYSQL ERROR:" + e.getMessage());
}

}
}

删除和更新数据都使用stmt.executeUpdate函数。
删除和更新数据都会返回一个Long的结果，如果为0，则删除或者更新失败，如果大于0则是操作删除的记录数

查询语句
package main;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;

public class Mysql {

/**
* 入口函数
* @param arg
*/
public static void main(String arg[]) {
try {
Connection con = null; //定义一个MYSQL链接对象
Class.forName("com.mysql.jdbc.Driver").newInstance(); //MYSQL驱动
con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/test", "root", "root"); //链接本地MYSQL

Statement stmt; //创建声明
stmt = con.createStatement();

//新增一条数据
stmt.executeUpdate("INSERT INTO user (username, password) VALUES ('init', '123456')");
ResultSet res = stmt.executeQuery("select LAST_INSERT_ID()");
int ret_id;
if (res.next()) {
ret_id = res.getInt(1);
System.out.print(ret_id);
}

//删除一条数据
String sql = "DELETE FROM user WHERE id = 1";
long deleteRes = stmt.executeUpdate(sql); //如果为0则没有进行删除操作，如果大于0，则记录删除的条数
System.out.print("DELETE:" + deleteRes);

//更新一条数据
String updateSql = "UPDATE user SET username = 'xxxx' WHERE id = 2";
long updateRes = stmt.executeUpdate(updateSql);
System.out.print("UPDATE:" + updateRes);

//查询数据并输出
String selectSql = "SELECT * FROM user";
ResultSet selectRes = stmt.executeQuery(selectSql);
while (selectRes.next()) { //循环输出结果集
String username = selectRes.getString("username");
String password = selectRes.getString("password");
System.out.print("\r\n\r\n");
System.out.print("username:" + username + "password:" + password);
}

} catch (Exception e) {
System.out.print("MYSQL ERROR:" + e.getMessage());
}

}
}

查询语句使用stmt.executeQuery函数

rs.absolute() //绝对位置，负数表示从后面数
rs.first()第一条
rs.last()最后一条
rs.previoust()前一条
rs.next()后一条
rs.beforeFirst()第一条之前
rs.afterLast()最后之后
rs.isFirst(),rs.isLast(),rs.isBeforeFirst(),rs.isAfterLast