mysql[Java]插入SQL时出错，在表userId中自动递增

Question

因此，我正在创建一个注册页面，当我输入所有字段并单击“注册”提交时，会调用enterNewUser（，，，）并将字段userId、username、password和role插入到User表中。我通过运行select*from user来确认这一点进入MYSQL工作台

然后调用enterUsername（，，，），我得到以下错误：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(3,'Barry','Allen')' at line 1 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(3,'Barry','Allen')' at line 1

public static int enterNewUser(String username,String password, String role){
    //int userId = -1;
    int ID = 0;
    //int ID=-1;
    try{
        if(checkUserNameAvailable(username)==true){
            Class.forName("com.mysql.jdbc.Driver");
            cn = DriverManager.getConnection("jdbc:mysql://localhost/log", "root", "root");

            String q0 = "Select userId from user ORDER BY userId DESC LIMIT 1"; //get ID of last
            Statement st = cn.createStatement();
            ResultSet rs = st.executeQuery(q0);

            if(rs.next()){

                ID = rs.getInt("userId");
                ID++;
            }
            else
                ID=1; // Empty Table, so start with ID 1

            rs.close();
            st.close();

            String q1="insert into user values(?,?,?)";

            PreparedStatement ps = cn.prepareStatement(q1);
            //ps.setInt(1,ID);
            ps.setString(1,username);
            ps.setString(2,password);
            ps.setString(3,role); 
            ps.executeUpdate();
            ps.close();

        }
    }catch(Exception e){
        System.err.println(e.getMessage());
        e.printStackTrace();
    }
    DB_close();
    //if(userId!=-1)
    //  return userId;
    return -1;      
}
public static boolean enterUsername(int userId, String firstname, String lastname){
    try{
        Class.forName("com.mysql.jdbc.Driver");
        cn = DriverManager.getConnection("jdbc:mysql://localhost/log", "root", "root");

        //String q1="INSERT INTO user_profile values(?,?,?)";
        String q1 = "INSERT into user_profile (userId, firstname, lastname) VALUES (?,?,?)";

        PreparedStatement ps = cn.prepareStatement(q1);
        ps.setInt(1, userId);
        ps.setString (1, firstname);
        ps.setString (2, lastname);
        ps.executeUpdate();
        ps.close();
        return true;
    }catch(Exception e){
        System.err.println(e.getMessage());
        e.printStackTrace();
    }
    DB_close();
    return false;
}

这是我的数据库结构

编辑：发现问题，数据库结构不正确

CREATE TABLE user ( userId int(3) NOT NULL AUTO_INCREMENT,
username varchar(20) DEFAULT NULL, password varchar(20) DEFAULT NULL, role varchar(20) DEFAULT NULL, PRIMARY KEY (userId),
UNIQUE KEY username (username) );

CREATE TABLE user_profile ( userId int(3) NOT NULL DEFAULT '0', firstName varchar(20) DEFAULT NULL, lastName varchar(20) DEFAULT NULL, PRIMARY KEY (userId), CONSTRAINT FK FOREIGN KEY (userId) REFERENCES user (userId) );

Answer 1

使用

String q1 = "INSERT into user_profile (firstname, lastname) VALUES (?,?)";

因为你的第一个字段是auto increment。。因此，它会在插入值时自动增加值

我建议这样

删除当前表并创建一个新表，如下所示

   id >int(30) (AUTO INCREMENT) NOTNULL  //Dont need to take care of this field

   USER_ID >int(30) NOT NULL  //you should create your own ID and increment it before adding a new person

   username >varchar(100)

   password >varchar(100)

   role >varchar(100)

通常，调用与代码完全相同的userId

String q0 = "Select userId from user ORDER BY USER_ID DESC LIMIT 1"; //get ID of last
        Statement st = cn.createStatement();
        ResultSet rs = st.executeQuery(q0);

        if(rs.next()){

            ID = rs.getInt("USER_ID ");
            ID++;
        }

Answer 2

不应该在方法enterUsername中包含以下部分

ps.setInt(1, userId);
ps.setString (1, firstname);
ps.setString (2, lastname);

像这样

 ps.setInt(1, userId);
 ps.setString (2, firstname);
 ps.setString (3, lastname);