Java SQL查询不使用Insert？

为什么不向表中添加更多数据？代码/查询有什么问题？数据库已连接并与Select*。。。 但是当我尝试使用Insert-into时，它给出了如下所示的错误，为什么？如何更正此错误

 public void RegisterNewUser(String username, String password, String firstname, String surname, String dateOfBirth, int currentWeight) {

    //This code will connect the database to the java program

    Connection myconObj = null; //allows to connect to database
    Statement mystatObj = null; // create statement (Execute queries)
    ResultSet myresObj = null; // get result
    ResultSetMetaData mymeta = null;

    try {

        String query = "INSERT INTO JACOVANSTRYP.MAINUSERDATA(USERNAME, PASSWORD, FIRSTNAME, LASTNAME, DATEOFBIRTH, CURRENTWEIGHTKG, ACTIVEPOINTS) VALUES(\"" + username + "\", \"" + password + "\", \"" + firstname + "\", \"" + surname + "\",\"" + dateOfBirth + "\", \"" + currentWeight + "0 )";

        myconObj = DriverManager.getConnection("jdbc:derby://localhost:1527/MainUserData", "jacovanstryp", "Eduplex1234");
        mystatObj = myconObj.createStatement();
        Statement add = myconObj.createStatement();
        add.executeUpdate(query);
        mymeta = myresObj.getMetaData();





        System.out.println("User Successfuly created");
    } catch (SQLException e) {
      e.printStackTrace();
    }

这是它给出的错误消息，我尝试在不使用从另一个类获取的值的情况下执行此操作，并且即使查询是在没有外部值的平面字符串中编写的，它仍然会给出相同的错误

    java.sql.SQLSyntaxErrorException: VALUES clause must contain at least one element. Empty elements are not allowed. 
    at org.apache.derby.client.am.SQLExceptionFactory.getSQLException(Unknown Source)
    at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
    at org.apache.derby.client.am.ClientStatement.executeUpdate(Unknown Source)
    at com.vanstryp.backend.commonMethods.RegisterNewUser(commonMethods.java:143)
    at com.vanstryp.GUI.Secure.Register.jButton1ActionPerformed(Register.java:389)
    at com.vanstryp.GUI.Secure.Register.access$400(Register.java:6)
    at com.vanstryp.GUI.Secure.Register$4.actionPerformed(Register.java:139)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
    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:6533)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
    at java.awt.Component.processEvent(Component.java:6298)
    at java.awt.Container.processEvent(Container.java:2236)
    at java.awt.Component.dispatchEventImpl(Component.java:4889)
    at java.awt.Container.dispatchEventImpl(Container.java:2294)
    at java.awt.Component.dispatchEvent(Component.java:4711)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
    at java.awt.Container.dispatchEventImpl(Container.java:2280)
    at java.awt.Window.dispatchEventImpl(Window.java:2746)
    at java.awt.Component.dispatchEvent(Component.java:4711)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    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: ERROR 42X80: VALUES clause must contain at least one element. Empty elements are not allowed. 
    at org.apache.derby.client.am.ClientStatement.completeSqlca(Unknown Source)
    at org.apache.derby.client.am.ClientStatement.completeExecuteImmediate(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.parseEXCSQLIMMreply(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.readExecuteImmediate(Unknown Source)
    at org.apache.derby.client.net.StatementReply.readExecuteImmediate(Unknown Source)
    at org.apache.derby.client.net.NetStatement.readExecuteImmediate_(Unknown Source)
    at org.apache.derby.client.am.ClientStatement.readExecuteImmediate(Unknown Source)
    at org.apache.derby.client.am.ClientStatement.flowExecute(Unknown Source)
    at org.apache.derby.client.am.ClientStatement.executeUpdateX(Unknown Source)
    ... 41 more

---

为7参数查询插入6个参数（检查最后的零）。 这是你应该做的：

  "INSERT INTO JACOVANSTRYP.MAINUSERDATA(USERNAME, PASSWORD, FIRSTNAME, LASTNAME, DATEOFBIRTH, CURRENTWEIGHTKG, ACTIVEPOINTS) VALUES(param1, param2, etc)"

参考：

因此，请尝试以下方法：

String query = "INSERT INTO JACOVANSTRYP.MAINUSERDATA(USERNAME, PASSWORD, FIRSTNAME, LASTNAME, DATEOFBIRTH, CURRENTWEIGHTKG, ACTIVEPOINTS) VALUES(\"" + username + "\", \"" + password + "\", \"" + firstname + "\", \"" + surname + "\",\"" + dateOfBirth + "\", \"" + currentWeight + ",0 )";

---

所选择的方法比查询本身有更多的错误。我已重写您的代码以使用PreparedStatement功能：

public void RegisterNewUser(String username, String password, String firstname, String surname, String dateOfBirth, int currentWeight) {

    //This code will connect the database to the java program

    Connection myconObj = null; //allows to connect to database
    ResultSet myresObj = null; // get result
    ResultSetMetaData mymeta = null;

    try {

        String query = "INSERT INTO JACOVANSTRYP.MAINUSERDATA(USERNAME, PASSWORD, FIRSTNAME, LASTNAME, DATEOFBIRTH, CURRENTWEIGHTKG, ACTIVEPOINTS) VALUES(?,?,?,?,?,?,?)";

        myconObj = DriverManager.getConnection("jdbc:derby://localhost:1527/MainUserData", "jacovanstryp", "Eduplex1234");
        PreparedStatement add = myconObj.prepareStatement(query);
        add.setString(1, username);
        add.setString(2, password);
        add.setString(3, firstname);
        add.setString(4, lastname);
        add.setString(5, dateOfBirth); // might need setDate() depending on your table structure
        add.setString(6, currentWeight);
        add.setString(7, "0");
        add.executeUpdate();
        mymeta = myresObj.getMetaData();
        System.out.println("User Successfuly created");
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

希望这有助于

---

@MarkRotterveel想解释一下OPs代码的错误。真的，没什么特别的。它可能会起作用，但在施工中需要更多的注意。此外，像OPs那样构造SQL会让他面临注入攻击。再说一次，这不是爱好项目的问题，但在专业背景下，您不想编写对SQL注入开放的代码。

使用parameterstry使用prepared语句重写，并使用Execute query而不是UpdateIt说executeQuery方法不能用于更新。最后一个零之前缺少逗号。-1表示不建议使用prepared语句，但是，你的建议甚至不起作用，因为最初的问题是使用双引号（用于引用对象名称）而不是单引号（用于文本），而不是使用双引号（用于引用对象名称）。您能解释一下原始方法的错误吗。mystatObj=myconObj.createStatement（）；这一行表示它需要将PreparedStatement转换为“mystatObj=（PreparedStatement）myconObj.createStatement（）；”当我这样做时，它会在线程“AWT-EventQueue-0”java.lang.ClassCastException:org.apache.derby.client.am.ClientStatement不能转换为java.sql.PreparedStatement“知道为什么吗？对不起，@jaco，只需取消mystatObjline@MarkRotteveel这与您希望的一致吗？我不会以“真的，没什么特别的”开头，因为原始代码中的SQL注入是一个巨大的安全漏洞。我也不会提到“这不是爱好项目的问题”，因为在爱好项目中学习的习惯和技巧通常也会在没有考虑专业背景的情况下应用。