com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: 主键重复入''。

Question

今天开始我遇到了这个异常，昨天还一切正常。以下是我的代码：

public void enterStaff() throws ClassNotFoundException, SQLException {
    try {
        Class.forName("com.mysql.jdbc.Driver");
        connect = DriverManager
                .getConnection("jdbc:mysql://localhost:3306/project?"
                        + "user=root&password=virus");
        statement = connect.createStatement();

        preparedStatement = connect
                .prepareStatement("SELECT count(*)FROM information_schema.tables\n"
                        + "WHERE table_schema = 'project' AND table_name = 'staff'");
        rs = preparedStatement.executeQuery();
        rs.next();
        int chk = rs.getInt(1);

        if (chk != 1) {
            preparedStatement = connect
                    .prepareStatement("create table staff (staffname varchar(30) primary key);");
            preparedStatement.executeUpdate();
        }

        preparedStatement = connect
                .prepareStatement("insert into staff values(?);");
        preparedStatement.setString(1, addSubName.getText());

        preparedStatement.executeUpdate();
    } catch (ClassNotFoundException | SQLException e) {
        throw e;
    } finally {
        close2();
    }

}

private void close2() {
    try {

        if (statement != null) {
            statement.close();
        }

        if (connect != null) {
            connect.close();
        }
    } catch (SQLException e) {

    }
}

我正在尝试创建一个只有一列且该列是主键的表格。第一次运行代码时，将创建表格。但是值未被输入。没有显示异常。但是当我尝试第二次输入值时，异常出现了。

如何纠正这个问题？如果有人需要查看更多代码，我会发布它。

这是用户输入数据的代码：

    addSubName = new TextField();
    addSubName.setPromptText("Staff Name");
    addSubName.setPrefSize(200, 30);

    final Button b2 = new Button("Add");
    b2.setFont(Font.font("Calibri", FontWeight.BOLD, 17));
    b2.setPrefSize(70, 30);
    b2.setStyle(" -fx-base: #0066ff;");
    b2.setTextFill(Color.BLACK);
    b2.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent e) {

            data.add(new Staff(addSubName.getText()));
            addSubName.clear();

            try {
                enterStaff();
            } catch (ClassNotFoundException ex) {
                Logger.getLogger(AddStaff.class.getName()).log(Level.SEVERE, null, ex);
            } catch (SQLException ex) {
                Logger.getLogger(AddStaff.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    });

异常详情为：

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '' for key 'PRIMARY'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1040)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4120)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4052)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2503)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2664)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2794)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2458)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359)
at addstaff.AddStaff.enterStaff(AddStaff.java:149)
at addstaff.AddStaff$2.handle(AddStaff.java:100)
at addstaff.AddStaff$2.handle(AddStaff.java:92)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
at javafx.event.Event.fireEvent(Event.java:171)
at javafx.scene.Node.fireEvent(Node.java:6867)
at javafx.scene.control.Button.fire(Button.java:179)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:193)
at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:336)
at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:329)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
at javafx.event.Event.fireEvent(Event.java:171)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3311)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3151)
at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3106)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2248)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
at com.sun.glass.ui.View.handleMouseEvent(View.java:530)
at com.sun.glass.ui.View.notifyMouse(View.java:924)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:17)
at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:67)
at java.lang.Thread.run(Thread.java:744)

- TomJ

---

你能让我们看到你插入的值吗？你的创建语句没有自增或类似的东西，所以也许插入的值出了问题。 - domdomcodecode

@d_ominic 我应该发布什么？ - TomJ

一些示例插入值，或者生成/确定插入语句中要放置的值的代码。 - domdomcodecode

您尝试通过文本框提交的值必须已经存在于表格中。您可能点击了“添加”按钮超过一次。 - Ravinder Reddy

我只按了一次按钮，我确定。 - TomJ

Answer 1

您应该在SQL查询中删除分号:

错误的查询：

prepareStatement("create table staff (staffname varchar(30) primary key);");

preparedStatement = connect.prepareStatement("insert into staff values(?);");

正确的查询语句是：

prepareStatement("create table staff (staffname varchar(30) primary key)");

preparedStatement = connect.prepareStatement("insert into staff values(?)");

检查您的插入查询

而且，我认为您在数据库中插入值的查询有误，只提到了表名，不应该提到列名。因此，您必须将表名添加到查询中。

错误的查询：

insert into staff values(?)

正确的查询：

    INSERT INTO table_name
    VALUES (value1,value2,value3,...);

---

refer this link:

http://www.w3schools.com/sql/sql_insert.asp

更新：1

错误代码：

statement = connect.createStatement();
preparedStatement = connect
                .prepareStatement("SELECT count(*)FROM information_schema.tables\n"
                        + "WHERE table_schema = 'project' AND table_name = 'staff'");
        rs = preparedStatement.executeQuery();
        rs.next();

你应该像这样更改：示例

Class.forName(driverName).newInstance();
con=DriverManager.getConnection(connectionUrl+dbName,user,password);
st = con.createStatement();
String sql="SELECT * FROM employees";
rs=st.executeQuery(sql);

注意：

1. 您不应该调用SQL查询。
2. 而且，您正在使用preparedStatement进行调用，您必须更改为statement
3. preparedStatement无法解析。

例如：

string sql=....sql query...;
statement.executeQuery(sql) 

更新：2：-->示例

public class User 
{
private String empname;
public String getEmpName()
{
    return empname;
}
public void setEmpName(String empname)
{
    this.empname=empname;
}

---

public void addUser(User user)
{
    try
    {
        PreparedStatement ps;
        ps=connection.prepareStatement("INSERT INTO employee (empname,empaddress,depname) VALUES (?,?,?)");
        ps.setString(1, user.getEmpName());
        ps.setString(2, user.getEmpAddress());
        ps.setString(3, user.getDepName());
        ps.executeUpdate();
    }
    catch(Exception e)
    {
        System.out.println(e);
    }
}

- jmail

---

@Tom，请检查这个答案。 - jmail

它没有起作用。你注意到异常了吗？它说主键有重复的值。异常是在第二次输入时出现的，而不是在第一次。这意味着数据没有被输入到数据库中。为什么数据没有被输入到数据库中呢？ - TomJ

在'b2.setOnAction(new EventHandler<ActionEvent>()'中，我首先写了'addSubName.clear();'。然后我写了'enterStaff()'方法。因此，在将数据插入表格时，它会自动获得一个空值。所以我先调用了'enterStaff()'方法，然后再调用'addSubName.clear()'方法。但这也没有起作用。 - TomJ

我该如何更改这个 - preparedStatement.setString(1, msg); - TomJ

user.getEmpName() 中 'user' 是什么意思？ - TomJ

Answer 2

可能导致此错误的原因是您试图将相同的值输入到表中的主键字段中。

例如，如果您有一个名为users的表，其中主键是user_id，并且您尝试输入以下内容：

INSERT INTO users ('user_id', 'name', 'age') VALUES (112233, 'Tom', 18);
INSERT INTO users ('user_id', 'name', 'age') VALUES (112233, 'Barry', 21);

会出现一个MySQLIntegrityConstraintViolationException: Duplicate entry错误。

注意：在某些情况下，需要在表中插入或更新列，在这种情况下，可以使用ON DUPLICATE KEY UPDATE。

例如：

INSERT INTO social_link ('user_id', 'social_id') VALUES (112233, 59874) ON DUPLICATE KEY UPDATE social_id=575123;

- Ithar