MySQL外键是一个复合键-什么语法?

有了InnoDB表,您可以:

create table YourTable (
     col1 int, 
     col2 int, 
     constraint foreign key (col1, col2) 
                references OtherTable (col1, col2) 
                on delete cascade
) type=InnoDB;

为了 MyISAM 表、外键约束被静默忽略。

for complete tutorial: http://dev.mysql.com/doc/refman/4.1/en/innodb-foreign-key-constraints.html