选择 where 查询的 JDBC 问题 [重复]

Question

我的代码：

con = jdbc.connect();
        System.out.println("status of con"+con);
String query = " select * from BmgCPUTotalUsage where CPUserID='"+CPUserID+"' and MessageTypeID='"+MessageTypeID+"'";
        System.out.println(query);
        PreparedStatement statement = con.prepareStatement(query);
    ResultSet result = statement.executeQuery();
    System.out.println(result);
    int QuotaUsed=result.getInt("QuotaUsed"); 

输出：

   status of concom.mysql.jdbc.JDBC4Connection@182600f
     select QuotaUsed from BmgCPUTotalUsage where CPUserID='msdp' and MessageTypeID='SMS'
    com.mysql.jdbc.JDBC4ResultSet@16e1dd8
    java.sql.SQLException: Before start of result set.

谁能告诉我如何删除这个异常。并从表中获取 QuotaUsed。其中 QuotaUsed 是一个整数。

Answer 1

您确实需要更多地阅读JDBC Tutorial，但简单来说，试试这个：

ResultSet resultSet = statement.executeQuery();
if (resultSet.next() {
    int quotaUsed = resultSet.getInt("QuotaUsed"); 
}