Java数据库连接（JDBC）
JDBC:Java DataBase Connectivity
MySQL SQLyog 和 Java客户端都可以和SQL进行交互
JDBC连接数据库的步骤
1.添加数据库驱动jar包支持
2.连接数据库
-username
-password
-connectionUrl
例如：
public static void testConnect() throws Exception
{
//连接MySQL服务器
String username = "root";
String password = "a1b2c3";
String connectionUrl = "jdbc:mysql://127.0.0.1:3306/af_school?useUnicode=true&characterEncoding=UTF-8";
Connection conn = DriverManager.getConnection(connectionUrl,username,password);
System.out.println("连接成功");
conn.close();
System.out.println("关闭连接");
}
JDBC查询数据
例如：
package my;
import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.ResultSet;
import com.mysql.jdbc.Statement;
public class Test
{
public static void testConnect() throws Exception
{
//连接MySQL服务器
String username = "root";
String password = "a1b2c3";
String connectionUrl = "jdbc:mysql://127.0.0.1:3306/af_school?useUnicode=true&characterEncoding=UTF-8";
Connection conn = DriverManager.getConnection(connectionUrl,username,password);
System.out.println("连接成功");
//数据库查询 Statement语句，ResultSet结果集
Statement stmt = (Statement) conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM student");
//如果有数据，则rs.next()为true
while (rs.next())
{
int id = rs.getInt("id");
String name = rs.getString("name");
String phone = rs.getString("phone");
Date birthday = rs.getDate("birthday");
System.out.println(id + "\t" + name + "\t" + phone + "\t" + birthday);
}
conn.close();
System.out.println("关闭连接");
}
public static void main(String[] args)
{
try
{
testConnect();
} catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
JDBC的插入数据
例如：
//连接MySQL服务器
String username = "root";
String password = "a1b2c3";
String connectionUrl = "jdbc:mysql://127.0.0.1:3306/af_school?useUnicode=true&characterEncoding=UTF-8";
Connection conn = DriverManager.getConnection(connectionUrl,username,password);
System.out.println("连接成功");
//插入数据
String sql = "INSERT INTO student(`id`,`name`,`birthday`)"
+ "VALUES(20181200,‘韩‘,‘1998-5-6‘)";
System.out.println("SQL:" + sql);
Statement stmt = (Statement) conn.createStatement();
stmt.execute(sql);
int count = stmt.getUpdateCount();
System.out.println("受影响的行数为：" + count);
conn.close();
System.out.println("关闭连接");
处理自增主键：
当主键设置为自增时，
1.插入数据时，不写该字段
2.执行时指定RETURN_GENERATED_KEYS
3.取出返回的自增主键
例如：
//插入一条数据
String sql = "INSERT INTO leave_event(`stuId`,`daysFrom`,`daysTo`,`type`,`reason`)"
+ "VALUES(20181010,‘2018-5-6‘,‘2018-5-20‘,‘1‘,‘出国‘)";
System.out.println("SQL:" +sql);
Statement stmt = (Statement) conn.createStatement();
stmt.execute(sql,Statement.RETURN_GENERATED_KEYS);
//取得自动生成的主键的值
ResultSet rs = stmt.getGeneratedKeys();
while (rs.next())
{
int id = rs.getInt(1);
System.out.println("产生的主键为：" + id);
}
JDBC的Statement接口提供的executeQuery executeUpdate execute三个方法的区别：
executeQuery：用于产生单个结果集的语句，利于SELECT语句
executeUpdate：用于执行INSERT DELETE UPDATE 以及SQL DDL（数据定义语言）语句
execute：用于执行返回多个结果集、多个更新计数或者二者组合的语句
