使用Statement查询数据
/**
* 连接数据库查询
* @author Administrator
*
*/
public class Test01 {
public static void main(String[] args) throws Exception {
//创建连接
Connection con=JDBC.getConnection();
//准备sql语句
String sql="select *from Student";
//命令对象
Statement stmt = con.createStatement();
//返回
ResultSet rs = stmt.executeQuery(sql);
while(rs.next()){
int no = rs.getInt("No");
String name = rs.getString("Name");
System.out.println(no+" "+name);
}
//关闭连接(后打开的先关闭)
rs.close();
stmt.close();
}
}
连接数据库.使用Statement登录
import java.sql.*;
import java.util.Scanner;
/**
* 登录
* @author Administrator
*
*/
public class Test02 {
public static void main(String[] args) throws Exception {
Connection con=JDBC.getConnection();
Scanner input=new Scanner(System.in);
System.out.println("请输入名字");
String name=input.next();
System.out.println("请输入密码");
int no=input.nextInt();
//sql语句
String sql="select *from Student where Name='"+name+"' and No='"+no+"'";
System.out.println(sql);
//命令对象
Statement stmt = con.createStatement();
/*PreparedStatement stmt = con.prepareStatement(sql);
stmt.setString(1,name);
stmt.setInt(2, no);*/
//处理结果
ResultSet rs = stmt.executeQuery(sql);
if(rs.next()){
System.out.println("欢迎");
}else{
System.out.println("登录失败");
}
//关闭连接(后打开的先关闭),释放资源
rs.close();
stmt.close();
}
}
Statement接口执行sql命令的三个方法:
ResultSet executeQuery(String sql):可以执行sql查询并获取ResultSet对象
int executeUpdate(String sql):可以执行插入,删除,更新的操作,返回值是受影响的行数
boolean execute(String sql):可以执行任意sql语句