小编Dan*_*iel的帖子

我正在尝试检查我的数据库中是否存在用户,然后为用户执行一些验证过程,如果没有返回入侵者消息.我正在使用Java和MySQL来达到这个目的.这是我的代码.

public class Check{

    public boolean isPresent(){
        connect();// private method that connects to db
        boolean isAvailable = false;
        String query = "SELECT EXISTS(SELECT 1 FROM students WHERE matric =" + this.myId + ")"; // this.myId has been passed into the constructor

        try{
            Statement statement;
            ResultSet resultSet;
            statement = connection.createStatement();
            resultSet = statement.executeQuery(query);
            if(resultSet.absolute(1)){
                isAvailable = true;
            }else{
                isAvailable = false;
        }catch(SQLException e){
            e.printStackTrace();
        }finally{
         closeConnection();// private method that closes connection
         return isAvailable;
    }

}

我已经检查过这样的解决方案,但似乎没有解决这个问题.我得到的错误是:"where子句中的未知列CCE",JDBC API中还有其他错误.在我看来,就像我从传承人那里传来的价值一样,有些东西被截断了.

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column …