jdb链接数据库，简单操作（ResultSet，浮标）（DriverManager 驱动管理器类 Connection 接口 Statement 接口）

链接数据库

  public static void main(String[] args) {
        //简约方式
        try {
            Connection conn = DriverManager.getConnection("jdbc:mysql:/mysql?user=aa");

            Statement st = conn.createStatement();
            ResultSet rs =st.executeQuery("show databases");

            while (rs.next()){
                System.out.println(rs.getString(1));
            }
            rs =st.executeQuery("select  version()");//结果集默认是开始前一个
            rs.next();
            System.out.println(rs.getString(1));
            rs = st.executeQuery("select *from db1.stu");
            while (rs.next()){
                System.out.printf("学号：%d，姓名：%s，成绩：%d分 \n",rs.getInt(1),rs.getString("name"),rs.getShort("score"));
            }

            rs.close();
            st.close();
            conn.close();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

     DriverManager 驱动管理器类

• Connection 接口

• Statement 接口

• public class StatementDemo {
      public static void main(String[] args) {
          try {
              Connection c =DriverManager.getConnection("jdbc:mysql:/db1?user=aa");
              Statement s =c.createStatement();
              System.out.println(s.execute("show tables"));//execute一般执行操作 建库、建表、删除
              //execute 有影响行、有结果的返回true值 ，没有的返回false Exception
  
              //对数据操作
              //ResultSet rs =s.executeQuery("select show");//返回结果集，查询时，返回ResultSet  插入 删除 修改
              //int rows= s.executeUpdate("insert datete update ");//返回影响行、查询
  
  
              //插入数据
  //            int n = s.executeUpdate("insert stu values (null ,‘李四‘,30),(null,‘aa‘,50),(null,‘mm‘,90)");
  //            System.out.println(n);
  
              //删除数据
  //            int n =s.executeUpdate("delete from stu where id in(12)");
  
              //修改表
  //            int up =s.executeUpdate("update stu set score=score+5");
  //            System.out.println(up);
  
              //批量语句 insert update delete 不能有查询语句select、crete datebesea
  //            s.addBatch("insert into stu values(null ,‘ttt‘,30),(null,‘jaav‘,98)");
  //
  //            s.addBatch("delete from stu where id=10");
  //            s.addBatch("delete from stu where id=2");
              int[] ns = s.executeBatch();
              for (int i:ns){
                  System.out.println(i);
              }
  
              //查询select show select 1,2,3;
  //            ResultSet rs = s.executeQuery("select 1,2,3*3");
                ResultSet rs =s.executeQuery("select *from stu");
  //            rs.next();
  
              while (rs.next()) {
                  System.out.printf("id:%d,name:%s,score:%d\n", rs.getInt(1), rs.getString(2), rs.getInt(3));
              }
              rs.close();
              s.close();
              c.close();
              } catch (SQLException throwables) {
              throwables.printStackTrace();
          }
  
      }
  }

  ResultSet，浮标

• public class StatementDemo2 {
      public static void main(String[] args) {
          try {
              Connection c = DriverManager.getConnection("jdbc:mysql:/db1?user=aa");
              Statement s =c.createStatement();
  
              ResultSet rs = s.executeQuery("select version()");
              rs.next();
              System.out.println(rs.getString(1));
  
  //            rs = s.executeQuery("select name,id,score as ss from stu where true order by score desc");
              Statement q = c.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);//添加游标操作
              rs = q.executeQuery("select name,id,score as ss from stu order by score desc");
  
              boolean ok = rs.isBeforeFirst();
              if(ok){
                  System.out.println("有数据");
                  rs.next();
                  rs.next();
                  System.out.println(rs.getString("id"));
                  rs.previous();
                  System.out.println(rs.getString("id"));
                  rs.last();
                  System.out.println(rs.isLast());
                  System.out.println(rs.getString("id"));
  
                  rs.absolute(4); //false 如果没有400条，指针指向最后一条记录之后。*跳转
                  rs.previous();
                  rs.previous();
                  System.out.println(rs.isLast());//看是不是在最后
                  System.out.println(rs.isAfterLast());//最后之后
                  System.out.println("-".repeat(50));
                  while(rs.next()){//*调转后从这里输出完
                      System.out.println(rs.getString("id"));
                  }
              }else{
                  System.out.println("没有结果");
              }
  
  //            while(rs.next()){
  //                System.out.printf("id:%d,name:%s,score:%d。\n",rs.getInt(2),rs.getString("name"),rs.getInt("ss"));
  //            }
  //
  //
  //
  //
  //
  //            System.out.println(rs.isBeforeFirst());//第一条记录之前
  //            System.out.println(rs.isFirst());//首先
  //            System.out.println(rs.isLast());//最后
  //            System.out.println(rs.isAfterLast());//在最后之后
  //            System.out.println(rs.next());//下一个
  //            System.out.println(rs.previous());//以前的
  //            System.out.println(rs.absolute(6));//绝对
  //            System.out.println(rs.first());//第一个
          } catch (SQLException throwables) {
              throwables.printStackTrace();
          }
      }
  }