mysql - 嵌套游标循环: Column count doesn't match value count at row 1

Question

这是我第一次在 MySQL 中处理游标和过程。我已按照 MySQL documentation on cursors 中给出的示例进行操作和 roseindia.net现在遇到错误:

Column count doesn't match value count at row 1

以下是涉及的表(这些表尚未标准化为 3NF，因为我收到的表是这样的，是的，我确实意识到我需要使用 arts.id 而不是 Artists.name):

CREATE TABLE `user_artists_rankings` (
  `user_id` varchar(50) NOT NULL DEFAULT '' COMMENT 'kpop_users.user_id',
  `artist_name` varchar(100) NOT NULL,
  `calculated_score` int(11) DEFAULT NULL,
  `last_calculated_score_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`user_id`,`artist_name`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
CREATE TABLE `kpop_users` (
  `user_id` char(50) NOT NULL,
  `username` char(150) DEFAULT '',
  `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`user_id`) USING BTREE,
  KEY `name_idx` (`username`),
  KEY `twitter_id_idx` (`twitter_user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;
CREATE TABLE `artists` (
  `name` varchar(100) NOT NULL,
  `type` varchar(45) DEFAULT NULL,
  `official_twitter_screenname` varchar(45) DEFAULT NULL,
  `thumbnail_url` varchar(500) DEFAULT NULL,
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`),
  KEY `Index_2` (`official_twitter_screenname`)
) ENGINE=InnoDB AUTO_INCREMENT=164 DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;

目标是在表中包含 user-artist(n) 行，user_artists_rankings，即:

user1 | artist1
user1 | artist2
user1 | artist3
user2 | artist1
user2 | artist2
user2 | artist3

这是我创建的过程:

delimiter ;
drop procedure if exists testrun;
delimiter //
create procedure testrun()
begin
    declare d int default 0;
    declare user_id varchar(50);
    declare artist_name varchar(100);
    declare cur_users cursor for select user_id from kpop_users;
    declare cur_artists cursor for select name from artists;
    declare continue handler for sqlstate '02000' set d=1;
    declare continue handler for sqlstate '23000' set d=1;
    open cur_users;
    open cur_artists;
    lbl1: loop 
        if d=1 then 
            leave lbl1;
        end if;
        if not d=1 then
            fetch cur_users into user_id;
            lbl2: loop
                if d=1 then
                    leave lbl2;
                end if;
                if not d=1 then
                    fetch cur_artists into artist_name;
                    insert into user_artists_rankings values (user_id, artist_name);
                end if;
            end loop lbl2;
        end if;
    end loop lbl1;
    close cur_users;
    close cur_artists;
end
//
delimiter ;
call testrun();

任何帮助将不胜感激。 谢谢。

Answer 1

这行代码是错误的:

insert into user_artists_rankings values (user_id, artist_name);

由于该表有 4 个字段，而您仅使用其中两个字段进行 INSERT，因此您需要指定使用哪些字段。应该是:

insert into user_artists_rankings(`user_id`, `artist_name`) VALUES(user_id, artist_name);