摘要：alter table 表名add constraint 外键名foreign key(字段名) references 主表名(字段名)on delete cascade语法：Foreign Key(column[,...n])references referenced_table_name[(ref_column[,...n])][on delete cascade][on update cascade]注释：column:列名referenced_table_name:外键参考的主键表名称ref_name:外键要参考的表的主键列on delete:删除级联on update:更新级联 阅读全文

摘要：（一）利用外键实现级联删除1、先建立测试数据库CREATE TABLE `roottb` ( `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL, `data` VARCHAR(100) NOT NULL DEFAULT '', PRIMARY KEY (`id`)) TYPE=InnoDB;CREATE TABLE `subtb` ( `id` INT(11) UNSIGNED AUTO_INCREMENT NOT NULL, `rootid` INT(11) UNSIGNED NOT NULL DEFAULT '0', 阅读全文