为什么不能添加这个外键？

Question

我有这个架构:

CREATE TABLE  `lotto`.`combinaciones` (
  `indice` mediumint(8) unsigned NOT NULL,
  `binario` int(10) unsigned NOT NULL,
  PRIMARY KEY  USING BTREE (`indice`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

CREATE TABLE  `lotto`.`sorteo` (
  `numeroSorteo` int(11) NOT NULL,
  `fechaSorteo` date NOT NULL,
  `precioCarton` double NOT NULL,
  `valorSerial` double NOT NULL,
  `valorMiniserial` double NOT NULL,
  `estatusSorteo` int(11) NOT NULL,
  `cantidadCartones` int(11) NOT NULL,
  PRIMARY KEY  (`numeroSorteo`),
  UNIQUE KEY `fechaSorteo` (`fechaSorteo`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

CREATE TABLE  `lotto`.`cartones` (
  `numeroSorteo` int(11) NOT NULL,
  `serial` mediumint(9) NOT NULL,
  `indice` mediumint(8) NOT NULL,
  `binario` int(11) NOT NULL,
  `miniserial` smallint(6) NOT NULL,
  `estatus` tinyint(4) NOT NULL default '0',
  PRIMARY KEY  (`numeroSorteo`,`serial`),
  KEY `new_index` (`indice`), -- ADD LATER
  CONSTRAINT `cartones_ibfk_1` FOREIGN KEY (`numeroSorteo`) REFERENCES `sorteo` (`numeroSorteo`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

我想添加这个:

ALTER TABLE `lotto`.`cartones` ADD CONSTRAINT `new_fk_56` FOREIGN KEY `new_fk_56` (`indice`)
    REFERENCES `combinaciones` (`indice`)
    ON DELETE RESTRICT
    ON UPDATE RESTRICT;

但INNODB一直抱怨没有找到一个指标:

Cannot find an index in the referenced table where the referenced columns appear as the first columns...

但它不是外键:combinaciones(indice)和外键一样sorteo(numeroSorteo)吗？,它正在发挥作用

编辑:

我已经测试了:KEY 'new_index' (indice )in not lotto.cartones和without.

Answer 1

`indice` mediumint(8) NOT NULL,

与...不是同一类型

`indice` mediumint(8) unsigned NOT NULL,

您需要同时使用indice无符号或无符号.