第十六天 SQL

SQL

数据库

DATABASE 数据库

TABLE 表

字段 （属性）

主键(primary key)：一个表中不能重复，能够使用这个值确定唯一一条数据

外键：一个表中的数据持有的其他表的值

package com.java.sql;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Test1 {
    public static void main(String[] args) {
        String driver="com.mysql.jdbc.Driver";
        String url="jdbc:mysql://localhost:3306/class";
        String user="root";
        String password="123456";
        try {
            Class.forName(driver);
            Connection con=DriverManager.getConnection(url,user,password);
            if(!con.isClosed()){
                Statement statement=con.createStatement();
                String insert="insert into student(id,name,sex,age)value(1,'张三',1,20)"; //增
                statement.execute(insert);
                String update="update student set age=25 where id=2";//改
                statement.execute(update);
                String delete="delete from student where name='李四'";//删
                String select="select * from student";
                ResultSet set=statement.executeQuery(select);
                set.first();
                while(!set.isAfterLast()){//查
                    System.out.println(set.getString("name"));
                    set.next();
                }
                System.out.println("执行成功");
            }else{
                System.out.println("打开数据库");
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

用户的注册与登录

package com.java.sql;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class SQLManager {
    private Statement statement;
    public Statement getStatement() {
        return statement;
    }
    public void setStatement(Statement statement) {
        this.statement = statement;
    }
    private static SQLManager manager;
    public static SQLManager newInstance(){
        if(manager==null){
            manager=new SQLManager();
        }
        return manager;
    }
    private SQLManager(){
        String driver="com.mysql.jdbc.Driver";
        String url="jdbc:mysql://localhost:3306/class";
        String user="root";
        String password="123456";
        try {
            Class.forName(driver);
            Connection con=DriverManager.getConnection(url,user,password);
            if(!con.isClosed()){
                statement=con.createStatement();
                statement.execute("create table if not exists user(num int not null primary key auto_increment,user_name varchar(20),password varchar(20))");//创建表
            }else{
                System.out.println("打开数据库");
            }
        }catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

注册

package com.java.sql;
public class Test2 {
    public static void main(String[] args) {
        SQLManager manager=SQLManager.newInstance();
    }
}

JButton btnNewButton = new JButton("注册");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String userName=textField.getText();
                String password=textField_1.getText();
                Statement state=SQLManager.newInstance().getStatement();
                String sql="select * from user where user_name='"+userName+"'";
                try {
                    ResultSet set=state.executeQuery(sql);
                    set.last();
                    int num=set.getRow();
                    if(num>0){
                        System.out.println("用户已存在");
                    }else{
                        String register="insert into user(user_name,password)values('"+userName+"','"+password+"')";
                        state.execute(register);
                        System.out.println("注册成功");
                    }
                } catch (SQLException e1) {
                    e1.printStackTrace();
                }
            }
        });

登录

JButton btnNewButton = new JButton("登录");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String userName=textField.getText();
                String password=textField_1.getText();
                Statement statement=SQLManager.newInstance().getStatement();
                String sql="select * from user where user_name='"+userName+"'and password='"+password+"'";
                try {
                    ResultSet set=statement.executeQuery(sql);
                    set.last();
                    int num=set.getRow();
                    System.out.println(num);

                } catch (SQLException e1) {
                    e1.printStackTrace();
                }
            }
        });