我正在尝试向数据库中的表添加外键。让我们考虑以下最小示例：

CREATE DATABASE db_foo;
USE db_foo;
CREATE TABLE a(b VARCHAR(3) PRIMARY KEY);
CREATE TABLE c(d VARCHAR(3), KEY c_ix (d));
ALTER TABLE c ADD CONSTRAINT fk_c_a FOREIGN KEY (d) REFERENCES a(b);

上面给出的代码在版本为5.0.95的MySQL服务器上运行得很好，但是当我在另一台运行MySQL版本5.7.12的服务器上运行它时，会出现以下错误：

ERROR 1142 (42000): REFERENCES command denied to user 'toto'@'xxx.xxx.xx.xx' for table 'a'

所以我的第一个猜测是检查我在两个服务器上是否有相同的权限。这是SHOW GRANTS;的输出：

MySQL 5.0.95服务器上：

+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Grants for toto@%                                                                                                                                                                            |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'toto'@'%' IDENTIFIED BY PASSWORD '*********'                                                                                          |
| GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE ON `db\_%`.* TO 'toto'@'%'  |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

MySQL 5.7.12服务器上：

+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Grants for toto@%                                                                                                                                                                                            |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'toto'@'%'                                                                                                                                                                             |
| GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, EVENT, TRIGGER ON `db\_%`.* TO 'toto'@'%' |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

我不知道为什么它会在一个案件中起作用，而在另一个案件中却不起作用，因为事实上，我似乎在两个案件中都有同样的特权。有什么建议吗？