Question

我需要将查询从数据库中获取的字符串分配给Jlabel。我尝试了很多方法但失败了。我该怎么办？

try{
  String sql="SELECT MAX(allocationID) FROM allocation where unit='"+ dept + " ' ";
  pst=conn.prepareStatement(sql);
  String x=  (pst.execute());
}
catch(Exception e){
}

Answer 1

需要研究在Java中连接数据库的步骤首先db steps 通过调用ResultSet rs = pst.execute();从声明中获取结果集使用resultset对象遍历行列表。之后，将值分配给JLabel。

Answer 2

你刚刚在你的小程序中犯了几个错误，看看下面的代码作为例子：

    // your way of using prepared statement is wrong.
    // use like this
    String sql="SELECT MAX(allocationID) FROM allocation where unit=?;"; 
    Connection conn = getConnection();
    PreparedStatement ps = conn.prepareStatement(sql);

    // assign values to the variables in the query string
    ps.setString(1, dept);

    // execute the query
    ResultSet rst = ps.executeQuery();

    // parse the result set to get the value
    // You'd better do some check here to ensure you get the right result
    rst.next();
    String x = rst.getInt(1) + "";

    ps.close();
    conn.close();
}

如果您有兴趣，请查看文章：https://docs.oracle.com/javase/tutorial/jdbc/basics/retrieving.html

如何将从数据库中获取的值分配给标签？

2 个答案: