Why "#1215 - Unable to add foreign key constraints" in SQL?

Question

SQL

I'm trying to import a table after moving to another host, but I get an error: #1215 - Unable to add foreign key constraints

CREATE TABLE `result_info` (
  `id` int(11) NOT NULL,
  `wk2_id` int(11) NOT NULL,
  `status` int(11) NOT NULL DEFAULT '0',
  `inc_all` decimal(16,2) NOT NULL DEFAULT '0.00',
  `exp_all` decimal(16,2) NOT NULL DEFAULT '0.00',
  `profit` decimal(16,2) NOT NULL,
  `comment` varchar(1000) COLLATE utf8_bin NOT NULL,
  `user_id` int(11) NOT NULL,
  `created_at` datetime NOT NULL,
  `changed_at` datetime NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

Answer 1

Here .

Answer 2

perhaps there is no primary key?