afdsf
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`web09`.`product`, CONSTRAINT `product_ibfk_1` FOREIGN KEY (`category_id`) REFERENCES `category` (`cid`))
主表不能删除，从表中已经引用的记录。
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`web09`.`product`, CONSTRAINT `product_ibfk_1` FOREIGN KEY (`category_id`) REFERENCES `category` (`cid`))
从表外键不能添加，主表中不存在的记录。
fadsfs