班级，专业就需要和班级表，专业表进行关联，但是在添加外键的过程中却出现了“Cannot add foreign key ...
First, it will go through the list of all tables in the given schema and create a dictionary of possible foreign key column names, according to a format string provided by the user. The format string has the%(table)sand%(pk)svariables replaced with the table name and primary key column ...
一、MYSQL中的约束 1、主键:primary key 唯一非空的特性并且可以优化查询速度 2、外键:foreign key 外键的作用保证2个或2个以上的数据表的数据一致性和完整性 3、唯一:unique 4、非空:not null 5、默认值:deafult 6、自增:auto_increment 设置了自增值每次自动增加1 二、外键的添加方式 1、方式一 create tab...
ALTER TABLE files ADD CONSTRAINT files_users_fk FOREIGN KEY(`user_id`) REFERENCES users(`id`) ON DELETE SET NULL ON UPDATE CASCADE; --
I'm using MySQL Administrator to create some foreign keys in a InnoDB database. The db is built around a 'many-to-one' design. I've tried creating keys to various tables but, I keep getting the 1005 error when I try to create them. I can create foreign keys if I link a col in...
根据索引的具体用途,MySQL 中的索引在逻辑上分为以下 5 类: 1) 普通索引 普通索引是最基本的索引类型,唯一任务是加快对数据的访问速度,没有任何限制。创建普通索引时,通常使用的关键字是 INDEX 或 KEY。 2) 唯一性索引 唯一性索引是不允许索引列具有相同索引值的索引。如果能确定某个数据列只包含彼此各不相同...
3.1.3通常MySQL自动地为主键创建一个索引primary。我们可以重新给这个索引起名: primary key index_primary(学号,课程号,毕业日期) 1. 3.2.1定义一个替代键: create table xs1 ( 学号varchar(6) null, 姓名varchar(8) not null unique, 出生日期 datetime ...
on creating a foreign key innodb should notice that an index for the column already exist. But we have had a bug here in older MySQL versions. 5.1.32 is very old ... actual version is 5.1.48. In actual version these bugs are fixed. My guess what happened on your system is that the...
Bug #39546 Create Foreign Key On Primary Key On same table Submitted: 19 Sep 2008 17:50Modified: 30 Nov 2009 16:08 Reporter: Bojan Vukasovic Email Updates: Status: Closed Impact on me: None Category: MySQL WorkbenchSeverity: S3 (Non-critical) Version: 5.0.27OS: Any Assigned to: ...
After creating several database table, I tried adding foreign key constraints (via Mysql query browser), but it failed. I used the following command to add a foreign key to the table column otherId, which references the ID of table "reftable": ALTER TABLE `test`.`testing` ADD CONSTRAINT...