课下作业（选做）第八周

课下作业（选做）第八周

相关知识点的总结（代码检查）

xampp 和数据库服务器建立连接 建立数据库 创建表 在idea上运行

结果截图（代码检查）

教材11.1-11.10的代码发分析

Example11_1

import java.sql.*; 
public class Example11_1 {
   public static void main(String args[]) {
      Connection con=null;
      //初始化
      Statement sql; 
      ResultSet rs;     
      //顺序查询，始终保持和数据库的连接，直到将对象中的数据查看完毕
      try{  Class.forName("com.mysql.jdbc.Driver"); //加载JDBC_MySQL驱动
      }
      catch(Exception e){}
      String uri = "jdbc:mysql://localhost:3306/students?useSSL=true";
      String user ="root";
      String password ="";
      try{  
         con = DriverManager.getConnection(uri,user,password); //连接代码
      }
      catch(SQLException e){ }
      try { 
          sql=con.createStatement();
          rs=sql.executeQuery("SELECT * FROM mess"); //查询mess表
          while(rs.next()) {   //读取数据
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s	",number);
             System.out.printf("%s	",name);
             System.out.printf("%s	",date); 
             System.out.printf("%.2f
",height);        
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println(e);
      }
  }
}

分析：查询students数据库中mess表中的全部记录

Example11_2

import java.sql.*; 
public class Example11_2 {
   public static void main(String args[]) {
      Connection con;
      Statement sql; 
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");   //连接数据库
      if(con == null ) return;
      //若数据为空
      try { 
          sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                                    ResultSet.CONCUR_READ_ONLY);  //为得到一个可滚动的结果集
          rs = sql.executeQuery("SELECT * FROM mess ");
          //根据参数ResultSet.TYPE_SCROLL_SENSITIVE和ResultSet.CONCUR_READ_ONLY的情况，sql返回相应类型的结果集
          rs.last();
          int max = rs.getRow();
          System.out.println("表共有"+max+"条记录,随机抽取2条记录：");
          int [] a =GetRandomNumber.getRandomNumber(max,2);//得到1-max之间2个不同随机数
          for(int i:a){
             rs.absolute(i);//油标移动到第i行
             String number = rs.getString(1);
             String name = rs.getString(2);
             Date date = rs.getDate(3);
             float h = rs.getFloat(4);
             System.out.printf("%s	",number);
             System.out.printf("%s	",name);
             System.out.printf("%s	",date); 
             System.out.printf("%.2f
",h);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println(e);
      }
  }
}

分析：随机查询student数据库中mess表的两条记录，首先将游标移动到最后一行，然后再获取最后一行的行号，以便获得表中的记录数目。

Example11_3

import java.sql.*; 
public class Example11_3 {
   public static void main(String args[]) {
      Connection con;
      Statement sql; 
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");//连接数据库
      if(con == null ) return;
      //若数据为空
      String c1=" year(birthday)<=2000 and month(birthday)>7";
      //条件1：若出生的年份在2000年或者2000年之前，月份在7月之后
      String c2=" name Like '张_%'";
      //条件2：学生姓张
      String c3=" height >1.65";
      //条件3：身高大于1.65
      String sqlStr =
      "select * from mess where "+c1+" and "+c2+" and "+c3+"order by birthday";
      //通过where查找和通过order by排序
      try { 
          sql=con.createStatement();
          rs = sql.executeQuery(sqlStr);
          while(rs.next()) { 
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s	",number);
             System.out.printf("%s	",name);
             System.out.printf("%s	",date); 
             System.out.printf("%.2f
",height);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println(e);
      }
  }
}

分析：
查询mess表中姓张，身高大于1.65，出生的年份在2000年或者2000年之前，月份在7月之后的学生，并按照出生日期排序。

Example11_4

import java.sql.*; 
public class Example11_4 {
   public static void main(String args[]) {
      Connection con;
      Statement sql; 
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");   //连接数据库
      if(con == null ) return;
      String jiLu="('R11q','王三','2000-10-23',1.66),"+
                  "('R10q','李武','1989-10-23',1.76)";    //插入的2条记录
      String sqlStr ="insert into mess values"+jiLu;
      //通过insert into mess values语句进行插入记录
      try { 
          sql=con.createStatement(); 
          int ok = sql.executeUpdate(sqlStr);
          rs = sql.executeQuery("select * from mess");
          while(rs.next()) { 
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s	",number);
             System.out.printf("%s	",name);
             System.out.printf("%s	",date); 
             System.out.printf("%.2f
",height);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println("记录中number值不能重复"+e);
      }
  }
}

分析：向mess中插入两条记录

Example11_5

import java.sql.*; 
public class Example11_5 {
   public static void main(String args[]) {
      Connection con;
      PreparedStatement preSql;  //预处理语句对象preSql
      ResultSet rs;
      con = GetDBConnection.connectDB("students","root","");  //连接数据库
      if(con == null ) return;
      String sqlStr ="insert into mess values(?,?,?,?)";
      //在对SQL进行预处理时可以使用通配符？来代替字段的值
      try { 
          preSql = con.prepareStatement(sqlStr);//得到预处理语句对象preSql
          preSql.setString(1,"A001");       //设置第1个?代表的值
          preSql.setString(2,"刘伟");       //设置第2个?代表的值
          preSql.setString(3,"1999-9-10"); //设置第3个?代表的值
          preSql.setFloat(4,1.77f);        //设置第4个?代表的值   
          int ok = preSql.executeUpdate();
          sqlStr="select * from mess where name like ? ";
          preSql = con.prepareStatement(sqlStr);//得到预处理语句对象preSql
          preSql.setString(1,"张%");       //设置第1个?代表的值
          rs = preSql.executeQuery();
          while(rs.next()) { 
             String number=rs.getString(1);
             String name=rs.getString(2);
             Date date=rs.getDate(3);
             float height=rs.getFloat(4);
             System.out.printf("%s	",number);
             System.out.printf("%s	",name);
             System.out.printf("%s	",date); 
             System.out.printf("%.2f
",height);
          }
          con.close();
      }
      catch(SQLException e) { 
         System.out.println("记录中number值不能重复"+e);
      }
  }
}

分析：使用预处理语句向mess表添加记录并查询了姓张的记录。

Example11_6

import javax.swing.*;
public class Example11_6 {
   public static void main(String args[]) {
      String [] tableHead;
      String [][] content; 
      JTable table ;//定义表格
      JFrame win= new JFrame();
      Query findRecord = new  Query();
      findRecord.setDatabaseName("students");
      findRecord.setSQL("select * from mess");
      content = findRecord.getRecord();
      //返回二维数组，即查询的全部记录
      tableHead=findRecord.getColumnName();
      //返回全部字段名
      table = new JTable(content,tableHead); 
      //表格JTable
      win.add(new JScrollPane(table));
      win.setBounds(12,100,400,200);
      win.setVisible(true); 
      win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   }
}

分析：将数据库的名字以及SQL语句传递给Query类的对象，用表格显示查询到的记录。

Example11_7

import java.sql.*; 
public class Example11_7{
    public static void main(String args[]){
       Connection con = null;
       //初始化
       Statement sql;
       ResultSet rs; 
       String sqlStr;
       con = GetDBConnection.connectDB("students","root","");  //连接数据库
       if(con == null ) return;
       try{ float n = 0.02f;
            con.setAutoCommit(false);       //关闭自动提交模式
            sql = con.createStatement();
            sqlStr = "select name,height from mess where number='R1001'";
            rs = sql.executeQuery(sqlStr);
            rs.next();
            float h1 = rs.getFloat(2);
            System.out.println("事务之前"+rs.getString(1)+"身高:"+h1);
            sqlStr = "select name,height from mess where number='R1002'"; 
            rs = sql.executeQuery(sqlStr);
            rs.next();
            float h2 = rs.getFloat(2);
            System.out.println("事务之前"+rs.getString(1)+"身高:"+h2);  
            h1 = h1-n;  //R1001的height的值减少n
            h2 = h2+n;  //将减少的n增加到字段是R1002的height上
            sqlStr = "update mess set height ="+h1+" where number='R1001'";
            sql.executeUpdate(sqlStr);
            sqlStr = "update mess set height ="+h2+" where number='R1002'";
            sql.executeUpdate(sqlStr);
            //更新数据
            con.commit(); //开始事务处理,如果发生异常直接执行catch块
            con.setAutoCommit(true); //恢复自动提交模式
            String s = "select name,height from mess"+
                      " where number='R1001'or number='R1002'";
            rs = 
            sql.executeQuery(s);
            while(rs.next()){
               System.out.println("事务后"+rs.getString(1)+
                                  "身高:"+rs.getFloat(2));  
            }
            con.close();
         }
         catch(SQLException e){
            try{ con.rollback();          //撤销事务所做的操作
            }
            catch(SQLException exp){}
         }
    }
}

分析：将mess表中number字段是R1001的height的值减少n，并将减少的n增加到字段是R1002的height上。

Example11_8

import java.sql.*;
public class Example11_8 {
   public static void main(String[] args) {
      Connection con =null;
      Statement sta = null;
      //初始化
      ResultSet rs;
      String SQL;
      try { 
        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");//加载驱动
      }
      catch(Exception e) {
        System.out.println(e);  
        return;
      }
      try { 
         String uri ="jdbc:derby:students;create=true";
         con=DriverManager.getConnection(uri);  //连接数据库
         sta = con.createStatement();
      }
      catch(Exception e) {
        System.out.println(e);  
        return;
      }
      try { SQL = "create table chengji(name varchar(40),score float)";
            sta.execute(SQL);//创建表
      }
      catch(SQLException e) { 
         //System.out.println("该表已经存在"); 
      }
      SQL ="insert into chengji values"+
            "('张三', 90),('李斯', 88),('刘二', 67)";
            //向表中添加三条新的记录
      try {
         sta.execute(SQL);
         rs = sta.executeQuery("select * from chengji "); // 查询表中的记录
         while(rs.next()) {
            String name=rs.getString(1);
            System.out.print(name+"	");
            float score=rs.getFloat(2);
            System.out.println(score);
         }
         con.close();
      } 
      catch(SQLException e) {
          System.out.println(e);  
      }
  }
}

分析：用Derby数据库管理系统创建了名为students的数据库，并在数据库中建立了chengji表

11章编程题：

参照例子3，按出生日期排序mess表的记录

import java.sql.*;
public class test1 {
    public static void main(String args[]) {
        Connection con;
        Statement sql;
        ResultSet rs;
        con = GetDBConnection.connectDB("students","root","");
        if(con == null ) return;
        String sqlStr =
                "select * from mess "+"order by birthday";
        try {
            sql=con.createStatement();
            rs = sql.executeQuery(sqlStr);
            while(rs.next()) {
                String number=rs.getString(1);
                String name=rs.getString(2);
                Date date=rs.getDate(3);
                float height=rs.getFloat(4);
                System.out.printf("%s	",number);
                System.out.printf("%s	",name);
                System.out.printf("%s	",date);
                System.out.printf("%.2f
",height);
            }
            con.close();
        }
        catch(SQLException e) {
            System.out.println(e);
        }
    }
}