如何在Java MySQL中计算数据 [英] How to count data in Java MySQL

问题描述

如何计算Java和MySQL中的数据？最终结果通过JOptionpane显示给我，但是我收到了一条带有此代码的错误消息。

How to count data in Java and MySQL? The final result is shown to me through JOptionpane but I got an error message with this code.

 try { DBConn.conn = DriverManager.getConnection(DBConn.Url, DBConn.User, DBConn.PWD);
          java.sql.Statement count = DBConn.conn.createStatement();
          String SQLCount = "select count(*) from datastudent where parklevel = 'Level 1' ";
                ResultSet rs = count.executeQuery(SQLCount);
                  while (rs.next()) {
                    JOptionPane.showMessageDialog(null,"number of existing parking is " + rs);
                }
            } catch (Exception e2) {
            //
            }
       } 

推荐答案

您应该打印 rs.getInt（1）。当您从某个表中选择某些数据的计数时，结果将作为结果集中的整数列返回。

You should print rs.getInt (1). When you select a count of some data from some table, the result is returned as an integer column in the result set.

请尝试：

JOptionPane.showMessageDialog（null，现有停车位数为+ rs.getInt（1））;

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