MySQL删除一些外键

我有一个表，该表的主键在其他几个表中使用，并且对其他表有几个外键。

CREATE TABLE location (
   locationID INT NOT NULL AUTO_INCREMENT PRIMARY KEY
   ...
) ENGINE = InnoDB;

CREATE TABLE assignment (
   assignmentID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   locationID INT NOT NULL,
   FOREIGN KEY locationIDX (locationID) REFERENCES location (locationID)
   ...
) ENGINE = InnoDB;

CREATE TABLE assignmentStuff (
   ...
   assignmentID INT NOT NULL,
   FOREIGN KEY assignmentIDX (assignmentID) REFERENCES assignment (assignmentID)
) ENGINE = InnoDB;

问题是，当我尝试删除外键列之一（即locationIDX）时，出现错误。

“错误1025（HY000）：重命名错误”

如何在没有出现此错误的情况下将列删除到上面的分配表中？