JDBC获得数据库生成的主键(JDBC、Primary Key)
JDBC获得数据库生成的主键 佟强 http://blog.csdn.net/microtong 在实际开发中,数据库中表的主键经常会由数据库负责生成,INSERT语句插入数据时插入除了主键以外的字段。很多情况下,当INSERT语句提交给数据库引擎执行完成后,程序需要获得生成的主键以便根
JDBC获得数据库生成的主键 佟强 http://blog.csdn.net/microtong
在实际开发中,数据库中表的主键经常会由数据库负责生成,INSERT语句插入数据时插入除了主键以外的字段。很多情况下,当INSERT语句提交给数据库引擎执行完成后,程序需要获得生成的主键以便根据主键查询插入的记录。JDBC通过在调用语句对象的executeUpdate()方法时,给出第二个参数Statement.RETURN_GENERATED_KEYS
来说明希望数据库引擎返回生成的主键。生成的主键以结果集的形式返回,程序调用语句对象的getGeneratedKeys()
方法得到一个结果集。遍历这个结果集,即得到数据库生成的主键。
我们以MySQL5.0数据库为例,创建会员表“member”,其中字段ID是数据负责生成的自动增量的整数。下列SQL语句创建会员表:
/* 创建MySQL5.0 表member*/
create table member(
id int not null auto_increment
, /*数据库自动生成的主键*/
name varchar(100), /*会员姓名*/
email varchar(255), /*电子邮件*/
primary key (id)
)type = InnoDB default character set gbk;
获得主键的代码 GeneratedKey.java
package cn.oakcms;
import java.sql.*;
public class GeneratedKey {
public static void main(String[] args) {
Connection conn = null; //连接对象
Statement stmt = null; //语句对象
ResultSet rs = null; //结果集
try{
//加载MySQL驱动程序
Class.forName("com.mysql.jdbc.Driver");
//连接字符串
String url = "jdbc:mysql://127.0.0.1:3306/mydb?useUnicode=true&characterEncoding=gbk";
//建立数据库连接
conn = DriverManager.getConnection(url,"root","");
//创建语句对象
stmt = conn.createStatement();
//INSERT语句
String sql = "insert into member(name,email) values('张三','zhangsan@gmail.com')
";
//执行INSERT语句,说明要返回数据库生成的主键
int count = stmt.executeUpdate(sql, Statement.RETURN_GENERATED_KEYS);
System.out.println("成功插入"+count+"条记录!");
//产生的主键以结果集的形式返回
rs = stmt.getGeneratedKeys();
//遍历结果集,输出主键,实际上结果集只有一条记录
while(rs.next()){
long id = rs.getLong(1);
System.out.println("产生的主键是:"+id);
}
//关闭结果集、语句、连接
rs.close(); stmt.close(); conn.close();
}catch(Exception e){
e.printStackTrace();
}finally{
if(rs!=null) try{rs.close();}catch(Exception ignore){}
if(stmt!=null) try{stmt.close();}catch(Exception ignore){}
if(conn!=null) try{conn.close();}catch(Exception ignore){}
}
}
}
程序的运行结果如下,每次运行都将插入一条新的记录,生成一个新的ID。
成功插入1条记录!
产生的主键是:6
OakCMS内容管理系统 http://www.oakcms.cn

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