20165302课下作业补做
课上作业补做
import java.sql.*;
public class Example11_1 {
public static void main(String args[]) {
Connection con=null;
Statement sql;
ResultSet rs;
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()) {//当存在下一个数据是返回true
String number=rs.getString(1);//将表第一列的数据传给number
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();//关闭连接
}
catch(SQLException e) {
System.out.println(e);
}
}
}
顺序查询，使用next（）方法移到下一个数据行，即游标位置。查询studen数据库中mess表的全部记录
import java.sql.*;
public class Example11_2 {
public static void main(String args[]) {
Connection con;
Statement sql;
ResultSet rs;
con = GetDBConnection.connectDB("students","root","");
if(con == null ) return;
try {
sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_READ_ONLY);
rs = sql.executeQuery("SELECT * FROM mess ");
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);
}
}
}
import java.sql.*;
public class GetDBConnection {
public static Connection connectDB(String DBName,String id,String p) {
Connection con = null;
String
uri = "jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
try{ Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
}
catch(Exception e){}
try{
con = DriverManager.getConnection(uri,id,p); //连接代码
}
catch(SQLException e){}
return con;
}
}
import java.util.*;
public class GetRandomNumber {
public static int [] getRandomNumber(int max,int amount) {
//1-max之间的amount个不同随机整数
int [] randomNumber = new int[amount];
int index =0;
randomNumber[0]= -1;
Random random = new Random();
while(index<amount){
int number = random.nextInt(max)+1;
boolean isInArrays=false;
for(int m:randomNumber){//m依次取数组randomNumber元素的值（见3.7）
if(m == number)
isInArrays=true; //number在数组里了
}
if(isInArrays==false){
//如果number不在数组randomNumber中:
randomNumber[index] = number;
index++;
}
}
return randomNumber;
}
}
将数据库连接的代码单独封装到GetDatabaseConnection类中，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
import java.sql.*;
public class Example11_3 {
public static void main(String args[]) {
Connection con;
Statement sql;
ResultSet rs;
con = GetDBConnection.connectDB("students","root","");
if(con == null ) return;
String c1=" year(birthday)<=2000 and month(birthday)>7";//条件1
String c2=" name Like '张_%'";
String c3=" height >1.65";
String sqlStr =
"select * from mess where "+c1+" and "+c2+" and "+c3+"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);
}
}
}
import java.sql.*;
public class GetDBConnection {
public static Connection connectDB(String DBName,String id,String p) {
Connection con = null;
String uri =
"jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
try{ Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
}
catch(Exception e){}
try{
con = DriverManager.getConnection(uri,id,p); //连接代码
}
catch(SQLException e){}
return con;
}
}
查询mess表中姓张，身高大于16.5，出生年份为2000或2000年之前，月份在七月份之后的学生，并按出生日期排序。
import java.sql.*;
public class Example11_4 {
public static void main(String args[]) {
Connection con;
Statement sql;
ResultSet rs;
con = GetDBConnection.connectDB("students","root","");
if(con == null ) return;
String jiLu="('R11q','王三','2000-10-23',1.66),"+
"('R10q','李武','1989-10-23',1.76)"; //2条记录
String sqlStr ="insert into mess values"+jiLu;
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);
}
}
}
向mess插入两条记录
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","");
if(con == null ) return;
String sqlStr ="insert into mess values(?,?,?,?)";
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);
}
}
}
import java.sql.*;
public class GetDBConnection {
public static Connection connectDB(String DBName,String id,String p) {
Connection con = null;
String uri =
"jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
try{ Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
}
catch(Exception e){}
try{
con = DriverManager.getConnection(uri,id,p); //连接代码
}
catch(SQLException e){}
return con;
}
}
使用预处理语句向mess表添加纪录并查询了姓张的记录
import javax.swing.*;
public class Example11_6 {
public static void main(String args[]) {
String [] tableHead;
String [][] content;
JTable table ;
JFrame win= new JFrame();
Query findRecord = new Query();
findRecord.setDatabaseName("students");
findRecord.setSQL("select * from mess");
content = findRecord.getRecord();
tableHead=findRecord.getColumnName();
table = new JTable(content,tableHead);
win.add(new JScrollPane(table));
win.setBounds(12,100,400,200);
win.setVisible(true);
win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
import java.sql.*;
public class Query {
String databaseName=""; //数据库名
String SQL; //SQL语句
String [] columnName; //全部字段（列）名
String [][] record; //查询到的记录
public Query() {
try{ Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
}
catch(Exception e){}
}
public void setDatabaseName(String s) {
databaseName=s.trim();
}
public void setSQL(String SQL) {
this.SQL=SQL.trim();
}
public String[] getColumnName() {
if(columnName ==null ){
System.out.println("先查询记录");
return null;
}
return columnName;
}
public String[][] getRecord() {
startQuery();
return record;
}
private void startQuery() {
Connection con;
Statement sql;
ResultSet rs;
String uri =
"jdbc:mysql://localhost:3306/"+
databaseName+"?useSSL=true&characterEncoding=utf-8";
try {
con=DriverManager.getConnection(uri,"root","");
sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_READ_ONLY);
rs=sql.executeQuery(SQL);
ResultSetMetaData metaData = rs.getMetaData();
int columnCount = metaData.getColumnCount();//字段数目
columnName=new String[columnCount];
for(int i=1;i<=columnCount;i++){
columnName[i-1]=metaData.getColumnName(i);
}
rs.last();
int recordAmount =rs.getRow(); //结果集中的记录数目
record = new String[recordAmount][columnCount];
int i=0;
rs.beforeFirst();
while(rs.next()) {
for(int j=1;j<=columnCount;j++){
record[i][j-1]=rs.getString(j); //第i条记录，放入二维数组的第i行
}
i++;
}
con.close();
}
catch(SQLException e) {
System.out.println("请输入正确的表名"+e);
}
}
}
将数据库名以及SQL语句传递给Query类的对象，用表格显示查询到的记录
import java.sql.*;
public class Example11_7{
public static void main(String args[]){
Connection con = null;
Statement sql;
ResultSet rs;
String sqlStr;
con = GetDBConnection.connectDB("students","root","");
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;
h2 = h2+n;
sqlStr = "update mess set height ="+h1+" where number='R1001'";
sql.executeUpdate(sqlStr);
sqlStr = "update mess set height ="+h2+" where number='R1002'";
sql.executeUpdate(sqlStr);
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){}
}
}
}
import java.sql.*;
public class GetDBConnection {
public static Connection connectDB(String DBName,String id,String p) {
Connection con = null;
String uri =
"jdbc:mysql://localhost:3306/"+DBName+"?useSSL=true&characterEncoding=utf-8";
try{ Class.forName("com.mysql.jdbc.Driver");//加载JDBC-MySQL驱动
}
catch(Exception e){}
try{
con = DriverManager.getConnection(uri,id,p); //连接代码
}
catch(SQLException e){}
return con;
}
}
将mess表中的number字段R1001的height值减少n，并将减少的n增加到字段是R1002的height上。
import java.sql.*;
public class Example11_8 {
public static void main(String[] args) {
Connection con =null;
Statement sta = null;
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)";
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);
}
}
}
这段代码的功能是使用了Derby数据库系统创建了名字是student的数据库，并在数据库中建立了chengji表