在 Java 中找不到列

Posted 2023-04-19

【中文标题】在 Java 中找不到列

【英文标题】：Column not found in Java

【发布时间】：2015-11-08 12:37:38

【问题描述】：

我在 Ms-Access 中有一个数据库表，名称为 CANDIDATE1、CANDIDATE2、CANDIDATE3、CANDIDATE4、CANDIDATE5。我有一个query，它在下面的代码中

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt)                                          
    // TODO add your handling code here:
    try
    
       String s = (String) jComboBox1.getSelectedItem();
        String sql = "SELECT '"+s+"' FROM results";
        rs = st.executeQuery(sql);
        while(rs.next())
        
            jLabel1.setText(rs.getString(s));
        
        JOptionPane.showMessageDialog(null,"U have voted "+jComboBox1.getSelectedItem()+",thank you!");

    
    catch(Exception e)
    
        JOptionPane.showMessageDialog(null,e);

    
        

当我尝试运行该程序时，它会抛出一个错误Column not found。我可以知道我的代码或查询有什么问题吗？

net.ucanaccess.jdbc.UcanaccessSQLException: Column not found: ADMK
at net.ucanaccess.jdbc.UcanaccessResultSet.getString(UcanaccessResultSet.java:689)  at 

net.ucanaccess.jdbc.UcanaccessResultSet.getString(UcanaccessResultSet.java:689)
    at pack.user_vote.jButton1ActionPerformed(user_vote.java:152)
    at pack.user_vote.access$000(user_vote.java:21)
    at pack.user_vote$1.actionPerformed(user_vote.java:87)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6525)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6290)
    at java.awt.Container.processEvent(Container.java:2234)
    at java.awt.Component.dispatchEventImpl(Component.java:4881)
    at java.awt.Container.dispatchEventImpl(Container.java:2292)
    at java.awt.Component.dispatchEvent(Component.java:4703)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
    at java.awt.Container.dispatchEventImpl(Container.java:2278)
    at java.awt.Window.dispatchEventImpl(Window.java:2739)
    at java.awt.Component.dispatchEvent(Component.java:4703)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
    at java.awt.EventQueue.access$400(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:697)
    at java.awt.EventQueue$3.run(EventQueue.java:691)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:719)
    at java.awt.EventQueue$4.run(EventQueue.java:717)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.sql.SQLException: Column not found: ADMK
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
    at org.hsqldb.jdbc.Util.sqlException(Unknown Source)
    at org.hsqldb.jdbc.JDBCResultSet.findColumn(Unknown Source)
    at org.hsqldb.jdbc.JDBCResultSet.getString(Unknown Source)
    at net.ucanaccess.jdbc.UcanaccessResultSet.getString(UcanaccessResultSet.java:687)
    ... 39 more
Caused by: org.hsqldb.HsqlException: Column not found: ADMK
    at org.hsqldb.error.Error.error(Unknown Source)
    at org.hsqldb.error.Error.error(Unknown Source)
    ... 43 more

注意：我使用ucanaccess 进行数据库连接。

【问题讨论】：

显示你的堆栈跟踪。

尝试打印sql字符串并用db检查该列是否存在？

显然，您从组合框中得到的任何内容都不是有效的列名。查看堆栈跟踪会很有帮助

【参考方案1】：

我认为您添加了无用的简单引号，应该是

String sql = "SELECT "+s+" FROM results";

（注意：您正在尝试从列中获取值，而不仅仅是字符串）

【讨论】：

我只能访问少数几列其他它说`用户缺乏特权或找不到对象`为什么会这样？

你能分辨出哪些吗？

我总共有 5 列，其中 1,2,5 不起作用。

您应该提供 SQL 架构和失败的列的名称。

我跟不上你，你能解释一下吗？