问题描述：往数据库的teachers表里面随机插入100万条带随机姓名，随机电话等字段的数据，需要多少秒？
接下来，我将从1.需要多少秒？2.为什么会这么快（包括PreparedStatement与Statement的区别）？两点进行编写。
一、需要多少秒
代码展示:
package com;
import java.sql.*;
import java.util.Random;
public class Demo4 {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
/**向数据库随机插入10000条数据**/
//1.加载驱动程序
Class.forName("com.mysql.jdbc.Driver");
//2.建立连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/class?","root","root");
//编写sql语句
String sql = "insert into teachers values(?,?,?,?)";
//编译
PreparedStatement ps = con.prepareStatement(sql);
int age;
//起始时间
long L1=System.currentTimeMillis();
for(int i=1;i<=1000000;i++){
//随机年龄
age= (int)(Math.random()*100+1);
ps.setInt(1,i);//字段1：id
ps.setString(2,getChilesName());//字段2：姓名
ps.setInt(3,age);//字段3：年龄
ps.setString(4,getTel());//字段4：电话
System.out.println("已经插入"+i+"条数据");
ps.addBatch();//addBatch()是把若干sql语句装载到一起,然后一次性传送到数据库执行,即是批量处理sql数据的。所以“冲突”得到解决,执行时间大大缩短。”
}
//结束时间
long L2=System.currentTimeMillis();
System.out.println(L2-L1);
con.close();
ps.close();
}
//获得随机姓名
public static String getChilesName(){
//百家姓(用数组的方式存取)
String[] family_name={
"赵","钱","孙","李","周","吴","郑","王","冯","陈","褚","卫","蒋","沈","韩","杨","朱","秦","尤","许",
"何","吕","施","张","孔","曹","严","华","金","魏","陶","姜","戚","谢","邹","喻","柏","水","窦","章","云","苏","潘","葛","奚","范","彭","郎",
"鲁","韦","昌","马","苗","凤","花","方","俞","任","袁","柳","酆","鲍","史","唐","费","廉","岑","薛","雷","贺","倪","汤","滕","殷",
"罗","毕","郝","邬","安","常","乐","于","时","傅","皮","卞","齐","康","伍","余","元","卜","顾","孟","平","黄","和",
"穆","萧","尹","姚","邵","湛","汪","祁","毛","禹","狄","米","贝","明","臧","计","伏","成","戴","谈","宋","茅","庞","熊","纪","舒",
"屈","项","祝","董","梁","杜","阮","蓝","闵","席","季","麻","强","贾","路","娄","危","江","童","颜","郭","梅","盛","林","刁","钟",
"徐","邱","骆","高","夏","蔡","田","樊","胡","凌","霍","虞","万","支","柯","昝","管","卢","莫","经","房","裘","缪","干","解","应",
"宗","丁","宣","贲","邓","郁","单","杭","洪","包","诸","左","石","崔","吉","钮","龚","程","嵇","邢","滑","裴","陆","荣","翁","荀",
"羊","于","惠","甄","曲","家","封","芮","羿","储","靳","汲","邴","糜","松","井","段","富","巫","乌","焦","巴","弓","牧","隗","山",
"谷","车","侯","宓","蓬","全","郗","班","仰","秋","仲","伊","宫","宁","仇","栾","暴","甘","钭","厉","戎","祖","武","符","刘","景",
"詹","束","龙","叶","幸","司","韶","郜","黎","蓟","溥","印","宿","白","怀","蒲","邰","从","鄂","索","咸","籍","赖","卓","蔺","屠",
"蒙","池","乔","阴","郁","胥","能","苍","双","闻","莘","党","翟","谭","贡","劳","逄","姬","申","扶","堵","冉","宰","郦","雍","却",
"璩","桑","桂","濮","牛","寿","通","边","扈","燕","冀","浦","尚","农","温","别","庄","晏","柴","瞿","阎","充","慕","连","茹","习",
"宦","艾","鱼","容","向","古","易","慎","戈","廖","庾","终","暨","居","衡","步","都","耿","满","弘","匡","国","文","寇","广","禄",
"阙","东","欧","殳","沃","利","蔚","越","夔","隆","师","巩","厍","聂","晁","勾","敖","融","冷","訾","辛","阚","那","简","饶","空",
"曾","毋","沙","乜","养","鞠","须","丰","巢","关","蒯","相","查","后","荆","红","游","郏","竺","权","逯","盖","益","桓","公","仉",
"督","岳","帅","缑","亢","况","郈","有","琴","归","海","晋","楚","闫","法","汝","鄢","涂","钦","商","牟","佘","佴","伯","赏","墨",
"哈","谯","篁","年","爱","阳","佟","言","福","南","火","铁","迟","漆","官","冼","真","展","繁","檀","祭","密","敬","揭","舜","楼",
"疏","冒","浑","挚","胶","随","高","皋","原","种","练","弥","仓","眭","蹇","覃","阿","门","恽","来","綦","召","仪","风","介","巨",
"木","京","狐","郇","虎","枚","抗","达","杞","苌","折","麦","庆","过","竹","端","鲜","皇","亓","老","是","秘","畅","邝","还","宾",
"闾","辜","纵","侴","万俟","司马","上官","欧阳","夏侯","诸葛","闻人","东方","赫连","皇甫","羊舌","尉迟","公羊","澹台","公冶","宗正",
"濮阳","淳于","单于","太叔","申屠","公孙","仲孙","轩辕","令狐","钟离","宇文","长孙","慕容","鲜于","闾丘","司徒","司空","兀官","司寇",
"南门","呼延","子车","颛孙","端木","巫马","公西","漆雕","车正","壤驷","公良","拓跋","夹谷","宰父","谷梁","段干","百里","东郭","微生",
"梁丘","左丘","东门","西门","南宫","第五","公仪","公乘","太史","仲长","叔孙","屈突","尔朱","东乡","相里","胡母","司城","张廖","雍门",
"毋丘","贺兰","綦毋","屋庐","独孤","南郭","北宫","王孙"};
//常见名(用字符串的方式存取)
String name1="楠明 裕昊 智棋 皓福 敬坤 渊荣 景尧 敬洪 朝实 善玮 朝棋 朝寒"+
" 楷林 景瑞 琪洋 捷杰 寒柏 敬易 涛光 鼎益 朝波 新明 昌震 皓翔"+
" 乔豪 敬轩 尚兴 皓清 裕明 杰宇 岩乐 乔宁 乔诚 川善 东辉 皓宁"+
" 雄杰 金锋 涛宇 楠峻 靖轩 尚欧 琪哲 皓景 昊辉 雨锋 智凯 捷旭";
//产生随机姓
int family_index=(int)(Math.random()*(family_name.length));
//产生随机名
//不能这样写，因为空格在字符串中也算字符，这样匹配到空格的话，就只有姓了
//int name_index=(int) (Math.random()*(name1.length()));//接下来用name1.charAt(name_index);
//正确方法：
//字符串分割(结果：字符串数组)
String[] first_name = name1.split(" ");//转换成字符串数组
int first_index = (int)(Math.random()*(first_name.length));
//产生随机姓名(字符串拼接)
String name=""+family_name[family_index]+first_name[first_index];
return name;
}
//获得随机电话
public static String getTel(){
int index;
String tel="1";
for(int i=1;i<=11;i++){
index =(int)(Math.random()*8)+1;
tel+=index;
}
return tel;
}
}
我们来看一下花了多长时间
结果很明显：四舍五入:15秒
看一下数据库中的teachers表是什么样的？
100万条数据（id,name,age,tel）已经插入了
ok,我们要知其然知其所以然，为什么只需要15秒呢？
二、为什么这么快
讲到为什么这么快，我们就要说到PreparedStatement与Statement的区别？
一、使用上的区别
- PreparedStatement语句中可以使用占位符代替某些字段
eg.
//编写sql语句
String sql = "insert into teachers values(?,?,?,?)";
//编译
PreparedStatement ps = con.prepareStatement(sql);
int age;
for(int i=1;i<=1000000;i++){
//随机年龄
age= (int)(Math.random()*100+1);
ps.setInt(1,i);//id
ps.setString(2,getChilesName());//姓名
ps.setInt(3,age);//年龄
ps.setString(4,getTel());//电话
System.out.println("已经插入"+i+"条数据");
ps.addBatch();
}
- Statement语句中的sql语句是字符串拼接，是不可变的，所以使用Statement必须一条一条的添加
eg. String sql = “insert into teachers values(1,“张三”,18,“18843421932”)”;
二、效率（性能）上的区别
1.PreparedStatement尽最大可能提高性能.语句在被DB的编译器编译后的执行代码被缓存下来,***那么下次调用时只要是相同的预编译语句就不需要编译,只要将参数直接传入编译过的语句执行代码中(相当于一个函数)就会得到执行.***这并不是说只有一个Connection中多次执行的预编译语句被缓存,而是对于整个DB中,只要预编译的语句语法和缓存中匹配.那么在任何时候就可以不需要再次编译而可以直接执行.
- 而statement的语句中,即使是相同一操作,而由于每次操作的数据不同所以使整个语句相匹配的机会极小,几乎不太可能匹配，并不是所以预编译语句都一定会被缓存,数据库本身会用一种策略,比如使用频度等因素来决定什么时候不再缓存已有的预编译结果.以保存有更多的空间存储新的预编译语句.
三、安全性上的区别
由于statement语句是将参数作为字符串拼接在sql语句中，如果有人恶意使用拼接，就有可能直接进入数据库，去操作数据。这种现象对于无论是公司还是个人都是无法容忍的。例如: 在sql语句的后面加上 “or 1=1”,有可能就可以获取所有的权限。在电商平台中，这样的情况下，去修改订单，操作订单。无论对于财务，库存，都是及其的不安全的。preparedStatement，语句，就可以单独的将参数用占位符代替。
总结：由前两点可知，PreparedStatement可以进行预编译，所谓的预编译就是语句在被DB的编译器编译后的执行代码被缓存下来,那么下次调用时只要是相同的预编译语句就不需要编译,只要将参数直接传入编译过的语句执行代码中(相当于一个函数)就会得到执行，所以它的效率比Statement高出很多，这也是为什么插入100万条数据才需要15秒的原因。
除此之外，1.如何随机插入中文姓名也要注意一下。2.随机名字不能使用字符串的形式，因为在字符串中空格也属于字符串。