java - 删除 MySQL 表 JDBC 中的特定项目

Question

我试图删除我的 MySQL 表中的特定项目:inventory，但是当我尝试执行此操作时，我不断收到 SQLException。

这是我的代码:

try
{
    Class.forName("com.mysql.jdbc.Driver");
    con = DriverManager.getConnection(url, root, password);
    statement = con.createStatement();

    int count = statement.executeUpdate(sqlQuery);
    String sqlQuery = "DELETE FROM inventory WHERE inventory ='?'";

    ps = con.prepareStatement(sqlQuery);
    ps.setString(1, item);
    count = ps.executeUpdate();
}catch(ClassNotFoundException e)
{
    e.printStackTrace();
}catch(SQLException e)
{
    e.printStackTrace();
}finally
{
    try
    {
        con.close();
        ps.close();
    }catch(SQLException e)
    {
        e.printStackTrace();
    }
}

这是我得到的错误:

 java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).
  at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:996)
  at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:935)
  at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:924)
  at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:870)
  at com.mysql.jdbc.PreparedStatement.checkBounds(PreparedStatement.java:3391)
  at com.mysql.jdbc.PreparedStatement.setInternal(PreparedStatement.java:3376)
  at com.mysql.jdbc.PreparedStatement.setInternal(PreparedStatement.java:3413)
  at com.mysql.jdbc.PreparedStatement.setNull(PreparedStatement.java:3452)
  at com.mysql.jdbc.PreparedStatement.setString(PreparedStatement.java:3954)
  at Inventory.deleteFromDatabase(Inventory.java:102)
  at Inventory$2.actionPerformed(Inventory.java:284)
  at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
  at javax.swing.AbstractButton$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)

如何修复此错误？谢谢!

Answer 1

如果您使用 PrepareStatement 来绑定(bind) String，您不需要在 周围加上单引号(表示字符串文字)？ - JDBC 驱动程序将为您处理输入。放下它们，你应该没问题:

String sqlQuery = "DELETE FROM inventory WHERE inventory = ?";